Developing a Project Base Map in ArcGIS · Developing a Project Base Map in ArcGIS ... Geog 480: Exploring Imagery and Elevation Data in GIS Applications ... on FTP servers, the file

Geog 480: Exploring Imagery and Elevation Data in GIS Applications Author: Karen Schuckman, [email protected]

Developing a Project Base Map in ArcGIS (30 points)

Introduction In this activity, you will be required to respond to objective questions, answer short essay questions, and upload screen captures to a Canvas quiz to get credit for your work. The procedure for uploading screen captures was introduced in the Orientation Lab. Canvas is set up to accept only one submission for this lab deliverable. All of the questions in the quiz deliverable are highlighted in bold red in these instructions. You should print a copy of these instructions to make notes as you perform the tasks. Save screen shots as you work. When you have completed the entire lab, enter your responses in the Canvas quiz and submit. If you have a technical problem with the quiz tool and need to resubmit, contact your instructor.

This lab activity will give you a chance to work with various forms of base map data, particularly imagery and elevation models, managing datums, map projections, and coordinate systems in ArcMap.

Many of the topics in this lab are covered in more depth in the ESRI Virtual Campus courses Learning ArcGIS Desktop (for ArcGIS 10) and Basics of Geographic Coordinate Systems. There is also a video, Coordinate Systems in ArcGIS: Tips and Tricks, which demonstrates useful problem solving methods for coordinate system-related problems. If at any time during this activity you feel you need additional explanation, refer to these additional resources.

Setup Before beginning the course work in earnest, we are going to check a few program settings in ArcMap to be sure we are all working with a consistent interface. ArcMap can be configured to minimize warnings of potential coordinate system problems. That configuration may save you a few mouse clicks when you are working with data you know to be error-free; however, it is a good idea to turn the warning system when working with data you are less familiar with. Let’s do that now, and you should leave these warnings turned on for the remainder of this course.

Find the Advanced ArcMap Settings Utility under the ArcGIS program installation folder, as shown below:

Double click on AdvancedArcMapSettings.exe to run the program.

Last Updated: 1/28/2018 12:43:00 PM Page 1 of 25

mailto:[email protected]

http://training.esri.com/gateway/index.cfm?fa=catalog.webCourseDetail&courseid=1942


http://www.uvm.edu/%7Ejoneildu/Video/GIS_Open/CoordinateSystems/CoordinateSystems.htm


Select the TOC/Data tab.

In the Working with data frame:

o Uncheck the option to Skip datum check

o Uncheck the option to Skip ‘Unknown Spatial Reference’ warning

o Check the option to “Warn when editing datasets with unmatched coordinate systems.”

Close the Advanced ArcMap Settings Utility.

Open ArcMap.

Data for the lab activities will be downloaded from a link in CANVAS in ZIP format, as explained below. The ZIP file is about 630 MB, uncompressed size is 970 MB.

On your hard drive, create a folder called Lesson2 which will be your working folder for all Lesson 2 lab activities. Remember, it is a best practice never to use spaces in the path to your data files!

Click on the Lesson 2 Lab Data link in the Lesson 2 folder in CANVAS and save the file Lesson2Data.zip in your Lesson2 folder. Extract the contents of the zip file into this folder. You should see subfolders for Part1, Part2, and Part3; Part1 and Part3 each contain a number of GIS data files; Part2 is empty. I recommend holding onto the ZIP file for now, in case you need to repeat a step in the activity with a fresh copy of the data.




Part 1: Common US Coordinate Systems (9 points) Browse to the Part1 folder and double-click on Lesson2_Part1.mxd to open it in

ArcMap. Your display should look like this:

Each data frame in an ArcMap map document should be assigned a coordinate system, which serves as the basis for all measurements and determines how data layers in that data frame are overlaid spatially in the map display. Data frame coordinate systems can be explicitly assigned by the user or, absent an explicit assignment, inherited from the first data layer added to the frame by default.

This map document has already been assigned a coordinate system. To find out what it is:

Right click on the data frame named Layers in the TOC pane. Choose Properties in the context menu that appears.

In the Data Frame Properties window, select the Coordinate System tab, and find the “Current coordinate system.” Scroll within the list of coordinate systems, and note that the current coordinate system is listed under the general heading of Geographic Coordinate Systems. This map document is currently assigned NAD 1983, a Geographic Coordinate System (GCS) that has been optimized for the North American continent. Notice that specific parameters for the map document coordinate system are given in the Data Frame Properties dialog box.




To answer the next several questions, rely upon your existing knowledge, refer to the free (no code required) ESRI VC course, Basics of Geographic Coordinate Systems, or read more about Geographic Coordinate Systems in the ArcGIS Help.

Q1: A geographic coordinate system is __________. Select the three phrases that correctly complete the sentence. (1 point)

A. flat

B. spheroidal

C. referenced to a constellation of stars

D. related to a datum

E. centered at the North Pole

F. centered at the approximate center of the Earth

G. a perfect representation of the surface of the Earth, including mountains and valleys

H. a map projection

Although shape of the Earth is generally spherical, there are many local irregularities; the Earth cannot be accurately represented for GIS purposes by the simple mathematical equation for a sphere. An ellipsoid or spheroid is a better general approximation of the Earth’s shape than a sphere. Based on centuries of surveys and measurements, many different spheroids have been developed to best fit a continent, country or a particular area of the Earth. A spheroid that best fits one region is not necessarily the same one that fits another region.

Q2: Which spheroid is the basis for the current map coordinate system (1 point)

A. World Geodetic System of 1984

B. Geodetic Reference System 1980

C. North American Datum of 1983

D. North American Datum of 1927

E. North American Vertical Datum of 1988

F. Clarke 1866 Spheroid

Click OK to dismiss the Data Frame Properties window.

Geographic data is often projected into a 2D rectangular coordinate system that has been optimized to fit a particular local area. The most commonly-used projected coordinate systems in the United States are UTM and State Plane. We will explore the borders and extents of these coordinate system zones in the next part of the lab exercise.

Make sure your display extent is the states layer by right clicking on the word “states” in the TOC, and selecting Zoom To Layer in the context menu that appears.

Now turn on the UTM Zones layer by clicking in the checkbox next to the layer name in the TOC.

As you zoom in, UTM zone numbers will appear as labels on the map. In this particular map layer, each UTM zone has further divided into rows that have letter designations. For most purposes (and to answer the following question), you should ignore the letter designations and use only the zone number to refer to a particular UTM coordinate system, with an “N” or “S” for the Northern or Southern Hemisphere. You can read more about the 10 UTM zones that cover the conterminous United States in the Geog 482 online textbook.




http://desktop.arcgis.com/en/desktop/latest/guide-books/map-projections/about-geographic-coordinate-systems.htm

https://www.e-education.psu.edu/natureofgeoinfo/c2_p22.html


Q3: How many UTM zones apply to the state of Pennsylvania? (1 point)

A. One

B. Two

C. Three

D. Four

Turn off the UTM Zones layer and turn on the State Plane Zones.

State Plane Zones are based on either Transverse Mercator or Lambert Conformal Conic projections, depending on the shape and orientation of the zone. You can also read more about State Plane zones and the underlying projections in the Geog 482 textbook.

Turn on the counties layer. You will have to zoom in to a scale greater than 1:5,000,000 to have the county boundaries appear in the map display.

Q4: True or False: State Plane Zones follow state and county boundaries in the conterminous United States. (1 point)

Q5: How many State Plane zones cover the state of Pennsylvania? (1 point)

A. One

B. Two

C. Three

D. Four

Transverse Mercator and Lambert Conformal Conic projections preserve conformality, which means that over small areas (within the confines of the particular projection) scale distortions are minimal. Measurements involving area and distance are accurate to within 1 part per 10,000 for State Plane zones, and 1 part per 1,000 for UTM.

When working on or near zone boundaries, one must make a choice of a working projection for the project. Some states, such as Michigan and Mississippi, develop a custom projection that encompasses the entire state rather than storing statewide data in two or more different zones (refer to the list of State Systems listed under Projected Coordinate Systems in ArcGIS). You will learn to discover, as well as to change, the coordinate system of a data layer later in this lab, a skill that is often needed when working with data layers from different sources.

One final layer that may be helpful when searching for data in the public domain is the index of 1:24,000 scale USGS topographic map sheets. Many federal and state agencies store their data in files corresponding to a USGS quadrangle or quarter-quadrangle.

Turn on the USGS 24k Map Sheets layer in the ArcMap TOC.

Zoom into Centre County, Pennsylvania at a scale greater than 1:500,000 so that the labels for the USGS layer are displayed.

USGS quadrangles are usually referenced by either name or an alphanumeric id code; on FTP servers, the file names always include one of these two references. You can always refer back to Lesson2_Part1.mxd to find quadrangle names and/or ids for any study area in the US.

Use the ArcMap Identify tool to query the USGS map sheet layer.



https://www.e-education.psu.edu/natureofgeoinfo/c2_p26.html


Q6: What is the quad id for the State College quadrangle? (1 point)

A. 39321609

B. 40077-G7

C. State College

D. 7752W 4052N

Finally, you may note that the shape of the United States, based on the GCS coordinate system, may not be what you are most used to seeing in published maps. You can easily change the data frame coordinate system to create a more aesthetically pleasing map.

Access the Coordinate System tab of the Data Frame Properties window.

Browse through the Predefined coordinate systems to select a Projected Coordinate System called US National Atlas Equal Area.

Q7: According to the ESRI metadata, what datum is the basis for the US National Atlas Equal Area map projection?

A. World Geodetic System of 1984

B. Geodetic Reference System 1980

C. North American Datum of 1983

D. North American Datum of 1927

E. North American Vertical Datum of 1988

F. Clarke 1866 Spheroid

G. GCS 1983

Q8: Which type of projection is used as the basis of the US National Atlas Equal Area coordinate system? (1 point)

A. Transverse Mercator

B. Lambert Conformal Conic

C. Lambert Azimuthal Equal Area

D. Albers

Apply the US National Atlas Equal Area coordinate system to the data frame. You should get the following warning.

This warning is generated because all of the other data layers in the map are based on the GRS80 ellipsoid rather than the ellipsoid of the map frame coordinate system. The mathematical calculations done by Arc to change the projection of the map layers in this case also involve a transformation between datums. ArcMap is asking you if you are sure you want to do this and




reminding you that you may be introducing error into your map if you continue. Whether or not that error is a concern depends on what you intend to do with the map. If you plan to make precise measurements or perform quantitative spatial analysis, the error may be a concern. If you are just using the map as an illustration, it’s usually okay to ignore the warning.

DO NOT check either of the “Don’t warn me” options. If you do check one of these options at some point during the course, use the Advanced ArcMap Settings Utility to restore the warning.

Now that you hopefully understand the nature of the warning, click Yes to continue.

Close the Data Frame Properties window, if open.

Q9: Turn off all layers in the map, except the states. Zoom to the full extent of the states layer in the US National Atlas Equal Area projection and make a screen capture of the map display. Upload your screen capture as the response to this question. Limit the width of your image to 800 pixels when inserting in the response box. (1 point)

Exit from ArcMap without saving.

Part 2: Using ESRI Basemaps (8 points) ESRI has created a number of global basemap layers that make it very easy for you browse an area of interest in ArcMap before you begin a project. As you might expect, there can be a price to pay for convenience, and in the case of the ESRI basemap there are consequences with respect to spatial accuracy that are related to the choice of the basemap coordinate system. As long as you understand what is happening behind the scenes, you should be able to be good decisions about how and when a particular basemap is appropriate for your project.

Open a new empty ArcMap document.

Use the Add Data pick list to select Add Basemap.

Add the Imagery basemap to your ArcMap document.

ESRI has chosen a special coordinate system for their global basemaps, called the WGS84 Web Mercator (Auxiliary Sphere), which is also used by Google, Bing, OpenStreetMap and other web-based mapping applications. It is a based on a perfect sphere rather than an oblate spheroid; is square (as you can see above); is made up of 256x256 smaller square tiles; and is optimized for delivery of cached raster images over the Web rather than for geometric accuracy.




The important thing to remember is that Web Mercator was selected for its efficiency in storage and delivery of massive quantities of data, not because it is a good map projection for map publication or spatial analysis. It does not minimize distortion of key spatial properties, such as area, distance, and direction. For example, the Polar Regions are represented at much larger scales than the equatorial regions, as you can easily see if you examine the basemap you have just loaded into ArcMap.

Because the Imagery Basemap was the first layer loaded into your blank map document, the data frame has inherited the Web Mercator coordinate system. Examine the data frame properties to answer the following questions:

Q10: Is Web Mercator a geographic coordinate system (GCS) or a projection? (1 point)

A. GCS

B. Projection

Q11: What are the default units of measurement for Web Mercator? (1 point)

A. Decimal degrees

B. Degrees, minutes, seconds

C. Feet

D. Meters

Save your map document in the Part2 folder, as Lesson2_Part2.mxd.

Use the Add Data button to add CentreCountyBoundary.lyr from the Part1 folder to your map document. This is a simple SHP containing one polygon, the boundary of Centre County, Pennsylvania where the Penn State University Park campus is located.

Close the coordinate system warning dialog to continue, if it appears.

Zoom to the extent of the Centre County boundary. Your map should look like the figure below. We have some very interesting topography in Happy Valley!

According to Wikipedia, Centre County has an area of 1,113 square miles. Let’s assume Wikipedia is a reliable source for basic information such as this, and let’s see what areas are calculated by ArcMap using several different map projections.

Right click on the CentreCountyBoundary layer in the ArcMap TOC to open the attribute table.

Add 2 new fields to the attribute table, called AREA_SP and AREA_WM. Define each of them as type FLOAT with precision of 16 (number of digits) and scale of 2 (number of decimal places).



http://en.wikipedia.org/wiki/Centre_County,_Pennsylvania


Right click on the heading for the column labeled AREA_SP and select Calculate Geometry.

Accept the warning about calculating outside of an edit session.

Select Area as the property to calculate, using the coordinate system of the data source, NAD83 Pennsylvania State Plane North.

Select units of Square Miles for the result.

Click OK, and accept the warning again.

Q12: True or False: Within a reasonable margin of error (< 1%), ArcMap calculates an accurate area for Centre County, PA based on the State Plane coordinate system. (1 point)

In the AREA_WM field, calculate the area of Centre County in square miles using the coordinate system of the data frame, Web Mercator.

Q13: True or False: Within a reasonable margin of error (< 1%), ArcMap calculates an accurate area for Centre County, PA based on the Web Mercator coordinate system. (1 point)

Save Lesson2_Part2.mxd, and exit ArcMap.

Let’s do a few more tests along the same lines using the map document you created in Part 1.

Open Lesson2_Part1.mxd.

Zoom to the Centre County boundary layer and open the attribute table.

Q14: Use Calculate Geometry to determine the area of Centre County using the GCS NAD 1983 coordinate system. Why can’t ArcGIS compute area in on a geographic coordinate system? (1 point)

Change the data frame coordinate system to one of the NAD83 UTM Zones that applies to Centre County.

Q15: True or False: Assuming the area stated in Wikipedia is correct, UTM coordinates produce a more accurate result than State Plane coordinates. (1 point)

Finally change the data frame coordinate system back to US National Atlas Equal Area as in Part 1.

Q16: True or False: Assuming the area stated in Wikipedia is correct, US National Equal Area coordinates produce a more accurate result than State Plane coordinates. (1 point)

Exit ArcMap.

You should now appreciate the fact that the choice of map projection for your basemap can have a significant impact on quantitative results produced from remote sensing analyses. You should, as a general rule, inspect all the data you intend to use in a project, think about the calculations you plan to perform, determine whether properties such as area and direction will affect the accuracy of your results, and then consciously choose the best coordinate system for your project basemap. For minimal distortion of multiple properties over a small project area (state, local, municipal), use a locally optimized projection, such as State Plane or UTM.

ESRI basemaps can be very helpful in the early stages of project set up and data browsing. The native Web Mercator projection allows for relatively quick loading, zooming and panning of the very large, web-hosted global dataset. If you bring an ESRI basemap into a data frame with a different map projection, such as UTM, ArcMap will reproject the basemap but display performance will be adversely affected. So, you may not want to force the ESRI basemap into a UTM or State Plane projection if you are just using it to get a quick overview of the project area. You may not need the ESRI basemap for more than a few steps at the beginning of your project.




In that case, you could work in Web Mercator while you are getting started with the ESRI basemap, then remove the ESRI basemap and change to the coordinate system of your choice before you begin performing quantitative analysis in earnest.

ArcMap also provides the option to perform geometry calculations on either the data frame coordinate system or the map layer coordinate system. If you are only using one or two data layers in your calculation, such as we did in the exercise above, you can use this option to ensure that you get correct calculation results. This strategy can work well if other data layers are simple SHP files; they will reproject much more quickly into Web Mercator than the ESRI basemap will reproject into State Plane. Just be sure you use the correct coordinate system option when calculating geometry.

When you start using large raster datasets, such as aerial orthophotos, USGS DEMs, Landsat images, or LAS datasets, allowing ArcMap to reproject-on-the-fly may have other important impacts. When working with a number of large datasets in a project, there may come a time when it makes sense to project the data into a common coordinate system before you load it into ArcMap.

Part 3: Creating a Basemap of the Penn State Campus (13 points) For the rest of this lab activity, you will be loading raster and vector data layers, including various types of imagery, elevation data, road centerlines, and USGS topo maps depicting the Penn State University Park campus in Centre County, PA. This will give you a chance to practice with the many types of data we will be using throughout this course, and it will help you get familiar with the landscape of your school! Some data will be given to you, some you will download from public sources. You can expect the data layers to be in a variety of coordinate systems and datums, some with complete and accurate coordinate system metadata and some without.

If you look back at Lesson2_Part1.mxd and zoom in on Centre County, PA, you will notice that we have a special case where, because of our location in the center of the state, we are bisected by the dividing line between UTM Zones 17 and 18 as well as PA State Plane Zones North and South. We are going to choose one of these coordinate systems for our project basemap, but we can expect to find data in public domain sources that comes in any one of these four coordinate systems.

Open ArcMap with an empty map.

As you know, the data frame in an empty map document has no assigned coordinate system. The data frame will inherit a coordinate system from the first layer added to the map, or the user can assign one before adding any data layers to the map. We know enough about our data now, and our study area, to make a good choice.

Using the Coordinate Systems tab in the Data Frame Properties window, select the following predefined coordinate system: Projected Coordinate Systems→State Plane→NAD 1983 (Meters)→NAD 1983 StatePlane Pennsylvania North FIPS 3701.

The FIPS code is simply a unique numeric identifier, issued by the National Institute of Standards and Technology; it is tied to the much longer text-based name but easier to use in computer programs and databases. Note the information that now appears in the “Current coordinate system:” text box, particularly the Linear Units which should be meters. State Plane projections are frequently created with units of feet, as indicated by the list of systems shown under State Plane in the coordinate system list. In general, you can choose the units that are most appropriate for your project.

Click OK to accept and close the Data Frame Properties dialog. You have now assigned a coordinate system to the data frame. If you reopen the Data Frame Properties dialog, the Coordinate System information should reflect your assignment.

Save Lesson2_Part3.mxd in the Lesson 2 Part 3 folder.




Individual data layers should contain information about their native coordinate system in metadata. ArcMap can display the data in the data frame coordinate system, performing the appropriate transformation on the fly, assuming it has all the necessary information to do so. It is not uncommon, even today, to find or be given datasets without appropriate projection information in an ESRI–compatible metadata format. It’s important for you to know how to manually examine and assign coordinate system information for individual datasets, and how to project a dataset from its native coordinate system to that of your map document. The best way to do this is to start by examining the metadata using ArcCatalog.

Recall that a projection is a mathematical transformation used to create a flat map from a curved surface. A geodetic model is a mathematical representation of that underlying curved surface. A map projection is tied to an origin defined in latitude and longitude, and the geodetic model defines the locations of those parallels and meridians relative to the physical earth. If the geodetic model is updated, then the map projections must also be updated. For example, map projections in the United States, such as State Plane and UTM, were originally based on the North American Datum of 1927. When the update to NAD83 occurred, new versions of the map projections were produced.

ArcMap can, invisibly to the user, transform from one map projection to another “on-the-fly” when a dataset is added, as long as the data frame and the individual dataset are based on the same geodetic model. If they are not, ArcMap will need more information from the user. The user should always know which version of the geodetic model and map projection were used to establish the coordinates of any dataset being used. Furthermore, as I said above, it’s not uncommon to receive incomplete or incorrect projection information. This activity will help you become more aware of what is going on “behind the scenes” and how to handle common problems.

Open ArcCatalog and browse to the Lesson 2 Part 3 folder.

Note first that there are two files called CentreCountyBoundary. One is a layer file containing preset symbology to control the way it is displayed in a map document. The second is an ESRI shapefile that contains the actual data.

Right click on the CentreCountyBoundary shapefile and select Properties. Under the XY Coordinate System tab, note the projected coordinate system, geographic coordinate system, and horizontal datum. This layer is already in the chosen basemap coordinate system.

View the Properties of centretopo100.img, which is not a shapefile but is a raster digital elevation model. The coordinate system information appears under the bold heading of Spatial Reference. You may have to scroll down to find this heading in the Raster Dataset Properties window. This layer is also already in the chosen basemap coordinate system.

Before adding any data to Lesson2_Part3.mxd, use ArcCatalog to find the spatial metadata for each of the remaining datasets. Remember that metadata is displayed differently for raster and vector datasets.

o local_roads.shp

o state_roads.shp

o naip_1-1_2n_s_pa027_2005_2.sid (a digital orthophoto from the USDA NAIP program)

o o40077g7.img (a scanned USGS topographic map)

Use the following set of choices to answer questions 17 through 20.

A. Pennsylvania State Plane North, meters, NAD 1983

B. Pennsylvania State Plane North, feet, NAD 1983




C. Pennsylvania State Plane North, meters, NAD 1927

D. Pennsylvania State Plane North, feet, NAD 1927

E. Pennsylvania State Plane South, meters, NAD 1983

F. Pennsylvania State Plane South, feet, NAD 1983

G. Pennsylvania State Plane South, meters, NAD 1927

H. Pennsylvania State Plane South, feet, NAD 1927

I. UTM Zone 18, meters, NAD 1983

J. UTM Zone 18, feet, NAD 1983

K. UTM Zone 18, meters, NAD 1927

L. UTM Zone 18, feet, NAD 1927

M. Coordinate system undefined

Q17: What are the native coordinate system, linear units, and horizontal datum for the vector dataset, local_roads.shp? (1 point)

Q18: What are the native coordinate system, linear units, and horizontal datum for the vector dataset, state roads.shp? (1 point)

Q19: What are the native coordinate system, linear units, and horizontal datum for the image dataset, naip_1-1_2n_s_pa027_2005_2.sid? (1 point)

Q20: What are the native coordinate system, linear units, and horizontal datum for the image dataset, o40077g7.img? (1 point)

Now that you have inspected the coordinate system metadata for each layer in your project, you will start adding the layers to the ArcMap document.

Add CentreCountryBoundary.lyr.

Add centretopo100.img. Note the High/Low values displayed in the TOC legend. We will come back to these later.

Add the NAIP image file. You may get a message from ArcMap asking if you want to build pyramids. If so, you may answer “yes.” Pyramids speed up zooming and panning actions in the display window for large image files.

Recall from your earlier inspection that NAIP image dataset is not natively in State Plane coordinates. Because the underlying datum (NAD83) is the same as that of the data frame, and the projection information for the image file is complete in the metadata, ArcMap can perform a coordinate transformation on-the-fly without a warning. It is not changing the native coordinate system of the image dataset; it is only projecting the image to the correct location in the map display coordinate system.

Note a few things about this image. First of all, it is a large mosaic made of many rectangular tiles, which were the original full resolution digital orthophoto quarter quadrangles. A raster file must, by definition, be rectangular – made up of a fixed number of rows and columns. The raster file holding the mosaic is a minimum bounding rectangle encompassing all of the component images, and areas having no valid information are filled in with pure black (RGB values = 0, 0, 0).

Also note that while the mosaic forms a rectangle, that rectangle is not orthogonal to the map coordinate system. This is because the mosaic is natively in one projected coordinate system (UTM) while the ArcMap data frame is in another (PA State Plane). The distortion of orientation is due to the re-projection of the image coordinate system, performed by ArcMap “on the fly” when you added the data layer. To convince yourself of this, try opening a new ArcMap project. Do not explicitly define a coordinate system for the data frame; load in just the image file. A new ArcMap




map document will, by default, inherit projection information from the first layer added. If you tried this, your result should look like the figure below:

The black background can be annoying if you are trying to create an overlay map with many data layers. You can make the black pixels “disappear” by making them transparent.

Right click on the image layer name in the ArcMap table of contents. Choose Properties, and then select the Symbology tab. Check the box next to “Display Background Value (R, G, B).” The default values should be 0, 0, 0. In the pull down menu next to the word “as,” choose “no color.” You are now telling ArcMap to display all pure black pixels in the image as transparent. If there are some legitimately pure black pixels within the aerial photo, they will also become transparent; however, it is unlikely that any “real” pixels are pure black.

Click OK. The black pixels should now be invisible.

Notice the ragged edge around the image boundary. This is caused by the compression algorithm used to create the Mr. Sid format. Along the edge, some of the pixels that should be pure black are just slightly non-black (see example below) due to the compression interpolation; therefore, they are not turned transparent.




Add the vector dataset, local_roads.shp. Use the zoom tool to examine the overlay of all the datasets. You can turn the display of individual layers on and off using the checkboxes in the TOC; you can also reorder the layers by dragging them up or down in the TOC. You should find that the roads line up correctly with the DEM and the image, even though all three are in different native coordinate systems.

Add the state_roads.shp dataset. You should get an error message from ArcMap saying, consistent with what you discovered in ArcCatalog, that there is no projection information. Click OK. ArcMap will draw the dataset in the display assuming that the coordinates are those of the data frame. You may have to use the Full Extent tool to see where ArcMap placed the dataset.

To get the state roads to appear in the correct location, we need to tell ArcMap what the native coordinate system is. Since it wasn’t provided as part of the metadata, you would have to find this out from whoever supplied the data. In this case, I supplied the data, and I am telling you now that the state roads are in the same native coordinate system as the local roads, except that the linear units are feet (US Survey Feet, not International Feet) instead of meters.

We are going to use the Define Projection tool in ArcToolbox to assign the correct coordinate system to the state roads. Open ArcToolbox using the icon on the Standard toolbar.

In the ArcToolbox menu, select Data Management Tools→Projections and Transformations→Define Projection.

Use the Define Projection tool to assign the correct native coordinate system to the state roads dataset. Then, ArcMap should be able to re-project the dataset on-the-fly into the correct location within the map display.

Next, we are going to bring in the scanned USGS topo map contained in the file, o40077g7.img. Use the Add Data button to add this dataset to the map. You may see




the pyramids message again. If so, answer either “yes” or “no” according to your preference.

You should see the Geographic Coordinate Systems Warning dialog box shown below:

3

If the warning box does not appear, remove the topo map from your map, save the document, exit ArcMap, and use AdvancedArcMapSettings.exe to reset the warning, as demonstrated at the beginning of this lab. Reopen Lesson2_Part3.mxd and add the topo map layer again.

In the warning box, click on the Transformations… button. You will see the dialog box shown below:

ArcMap knows that the incoming dataset is in NAD27, so in the Convert From field, GCS_North American_1927 should automatically be highlighted. ArcMap also knows that the data frame is in NAD83, so in the Into field, GCS_North_American_1983 should automatically be selected. Pull down the list of options given for the Using field.

A number of geodetic transformations have been developed between NAD27 and NAD83 for various regions of North America. For locations within the contiguous 48 US states, the NADCON transformation is the appropriate one to use. It should be at the top of the list. Select it now.




Click OK to accept and Close the Geographic Coordinate warning. The scanned topo map should be imported to the ArcMap map document.

Right click on o40077g7.img in the TOC. Select Zoom to Layer. Examine the overlay of this scanned topo map relative to other map layers.

Create a map display that clearly shows all of data layers listed below. This does not have to be a “pretty map,” but each of the data layers must be visible and it must be clear that they are correctly georeferenced.

o NAIP image

o DEM

o scanned topo map

o local roads

o state roads

Q21: Create a screenshot of the entire ArcMap application window. Upload your screen capture as the response to this question. Limit the width of your image to 800 pixels when inserting in the response box. (1 point)

Loading an Image Mosaic Dataset In version 10.0 and beyond, ESRI has developed powerful tools for managing and displaying large raster datasets in an ArcMap document. You will learn how to create a mosaic dataset later in the course. For now, you will load one that was included in the lab data package.

Add the PAMAPOrthophotos image mosaic from the Lesson2Part3.gdb geodatabase found in the Part3 folder.

Move PAMAPOrthophotos in the TOC so it is above all the other raster data layers, but below the Centre County boundary, and the state and local roads.

Zoom in to the extent of the image mosaic. Notice that the mosaic dataset contains 3 features: a boundary, outlines of the footprints of the 4 images that make up the mosaic, and the imagery itself.




Turn off the boundary and the footprints in the display.

Zoom and pan in the image to find landmark features on the Penn State campus, such as Beaver Stadium, the Bryce Jordan Center, the baseball stadium, Old Main and so on. Use resources such as Google Earth, MapQuest, or http://www.geog.psu.edu/print-campus-maps to help you located these named features.

Use the Identify tool to query the state road layer in order to answer the next question.

Q22: What is the name of the street that runs SW to NE past Beaver Stadium, intersecting the highway interchange at the northern edge of the image mosaic? (1 point)

A. Fox Hollow Road

B. Park Avenue

C. Beaver Avenue

D. Paterno Way

Query the image mosaic metadata in order to answer the next question.

Q23: What is the ground sample distance (GSD) of a single pixel in the PAMAP Orthophoto imagery? (1 point)

A. 1 foot

B. 1 meter

C. 3 feet

D. 3 meters

E. 1 arc second

Browsing Lidar Data in ArcGIS In ArcCatalog, create a new LAS Dataset, called PAMAP_Lidar.lasd, in your Lesson 2

Part 3 folder.



http://www.geog.psu.edu/print-campus-maps

http://www.geog.psu.edu/print-campus-maps

https://en.wikipedia.org/wiki/Ground_sample_distance


Right click on PAMAP_Lidar.lasd to access the Properties dialog.

On the Files tab, add the contents of the folder PAMAP_Lidar (4 individual LAS files) to the LAS dataset.

Add the LAS Dataset called PAMAP_Lidar to the ArcMap document. It should cover exactly the same area as the PAMAP Orthophoto mosaic.

Zoom to the extent of PAMAP_Lidar. You may not see anything in the display at this point, because the lidar point dataset is so large that it will not display at this zoom level. Zoom in until you can see the individual lidar points.

Turn off the display of the lidar data for the moment, by unchecking the layer in the TOC.

Pan to the location of Beaver Stadium, at a scale of 1:1,500.

Turn on the lidar layer. Your display should look like this:

Notice in the legend that the points are displayed with a color according to LAS point elevation. Note the minimum and maximum values. Recall the minimum and maximum values displayed for the USGS DEM (centretopo100.img). The USGS DEM covers a much larger area than the lidar, so it’s not surprising that the range of elevations found in the DEM would be greater than those found in the lidar layer. The lidar data only covers a small portion of campus within the extents of the USGS DEM, and the USGS DEM includes the Nittany Mountain range as well as Spring Creek Canyon. But certainly the range of elevations in lidar layer should be contained within the range of elevations for the DEM. According to the legend, that is not true. What is going on?

Q24: What are the vertical units for the USGS DEM? (1 point)

A. Meters

B. Centimeters

C. Feet

D. Degrees

Use ArcCatalog to query the properties of the LAS dataset. Because lidar data is three-dimensional data, there should be a vertical as well as a horizontal coordinate system associated with it.




Q25: What are the vertical units for the LASDataset? (1 point)

A. Meters

B. Centimeters

C. Feet

D. Degrees

Notice that while vertical units are defined in the layer properties, the information seems a little incomplete. That is because this lidar data was originally created for the PAMAP program before ESRI established its metadata requirements for 3D data in ArcGIS. So the metadata in the LAS files are incomplete from ArcMap’s perspective. We can fix that now.

Assign NAVD 1988 (US Survey Feet) as the Z coordinate system for PAMAP_Lidar.lasd

Return to ArcMap and query the elevation for a point (using the Identify tool) in Breaver Stadium parking lot, or on the football field, in both PAMAP_Lidar and centertopo100.img. The lidar data is much more recent, at much higher resolution, and more vertically accurate than the USGS DEM. It would be reasonable to find discrepancies on the order of a meter or so in areas that have not changed over time. There may be larger discrepancies if actual changes have occurred in a local area, such as the building of a new building, road, or parking lot.

You should also be asking yourself about the maximum elevation in the lidar dataset, 4782. Do you think there is a physical object within its extents that is at this elevation?

If you have ever worked with lidar data in LAS format, you should know that all points that were originally collected by the sensor are contained in the LAS file. Points are never deleted, they are only tagged and put onto various classes according the point type. Let’s look at the classified lidar data now.

Open the LAS Dataset toolbar in ArcMap. Make sure you also have Spatial Analyst and 3D Analyst checked (turned on) under the Customize→Extensions menu or the LAS Toolbar will not be active.

Change the point symbology to Class using the button to the right of the layer name in the LAS Dataset toolbar. Now examine the legend in the TOC. Color symbols now correspond to classes of points. For the PAMAP project:

o Class 1: unassigned – all non-ground points, including trees, buildings, light poles, etc.

o Class 2: Ground – bare earth surface

o Class 7: Noise – points that have anomalously high or low elevations. It is normal to have some noise in a lidar dataset; the origin and classification of noise points are covered our online course: Topographic Mapping with Lidar. It is not unusual to have a few very high points resulting from lidar hits on birds or even clouds.

o Class 8: Model Key – a special type of bare ground point. This is also covered in our online course: Topographic Mapping with Lidar.

o Class 9: Water – water bodies require special treatment in DEM creation; therefore, lidar points on water bodies are classified as such in most public domain lidar datasets.

Find Beaver Stadium and set your map scale to 1:1500, with the lidar points colored by class.




Use the LASDataset 3D View tool to create a view of Beaver Stadium as seen by a person standing on the ground, at a map scale of 1:1500, with lidar points colored by class.

Q26: Create a screen capture of the 3D view of Beaver Stadium and upload it as the response to this question. Limit the width of your image to 800 pixels when inserting in the response box. (1 point)

Close the 3D View window.

Save Lesson2_Part3.mxd.

Part 4: Browsing Landsat Imagery in ArcGIS As the last activity in this lab, you are going to download some Landsat Look imagery from the USGS Earth Explorer website. Note: If you find the hyperlinks below are not working correctly, make sure you are not viewing these instructions within CANVAS. If you need more help understanding the EarthExplorer interface, check out the USGS Help Documentation. If you do not already have one, create a USGS EROS web services account.

Open EarthExplorer in your web browser.

Login using the button at upper right.

On the Search Criteria tab, enter “Beaver Stadium” as the Address/Place. Click Return to Search. Beaver Stadium should come up in the Address link. Click the link and you should see a red marker come up in the map display at the right location.

On the Data Sets tab, select all three options under Landsat Archive Collection 1 Level 1.

On the Additional Criteria tab, select the following options for all 3 selected data sets.

o Less than 10% Land Cloud Cover

o Level 1TP Data Type (orthorectified)

Click Results to see your selection.

Find the following cloud-free Landsat images over Centre County, PA. Note the designation L1T in the metadata that indicates each of these images has been terrain-corrected (orthorectified).

o Landsat 5 TM, April 17, 2009

o Landsat 7 ETM, March 24, 2009

o Landsat 8 OLI, October 21, 2013

Add all three data sets to your shopping cart by clicking the Bulk Download icon, as shown below. If you have difficulty using the Bulk Download application (which requires Java), try downloading the files individually using the icon immediately to the left of Add to Bulk Download.

Proceed to View Item Basket.

Expand the Bulk Download data set for L4-5. Examine the product options. You can read more about Landsat Look images on the USGS website.

o Landsat Look: Natural Color and Landsat Look: Thermal. These are fairly small (~5 MB) thumbnails of the full image that can be downloaded as simple image files and used for graphic purposes. They do not contain any georeferencing metadata, so they are of no use in ArcMap.



https://earthexplorer.usgs.gov/documents/helptutorial.pdf

https://ers.cr.usgs.gov/login/

https://earthexplorer.usgs.gov/

http://landsat.usgs.gov/LandsatLookImages.php


o Landsat Look Images with Geographic Reference: These are the same thumbnail images as above, in a format that includes georeferencing information so they can be loaded into GIS in their proper location. They are a lower resolution product than the full Landsat and do not contain all of the spectral channels. They are not appropriate for image analysis purposes, but they are useful as a preview of the full resolution dataset and can be downloaded quickly because of the small size.

o Landsat Level 1 Product: full resolution data with all spectral channels included. Level 1 products with the L1T designation are also terrain corrected. This is the product to use for image analysis, but note the large size! These files may take quite a while to download, so it’s often a good idea to use the smaller Landsat Look images to preview the scene before downloading the Level 1 product.

Select ONLY the zipped Landsat Look Images with Geographic Reference for each of the three images in your cart into this folder.

Proceed to Checkout.

Check the file sizes for the items in your order. The total should be 47.7 MB if you have selected the correct products.

Submit your order.

Check your email for a USGS Online Bulk Download Order Confirmation from USGS/EROS.

Download and install the Bulk Download Application (BDA) according to instructions provided in the email.

Run BDA to access your order.

Click the small folder icon to change the default download destination.

Make a folder called Landsat under your Lesson2 folder.

Download all three data sets.

Unzip the compressed files into the Landsat folder and examine the contents. There are three versions of each scene in .tif format:

o “natural” looking 3-band composite false color image

o single-band greyscale thermal band image (TIR)

o 8-bit quality image (QB).

Open Lesson2_Part3.mxd in ArcGIS.

Turn off both vector road layers in the TOC.

Turn off the USGS topo map, the USGS DEM and the NAIP aerial photo mosaic in the TOC.

Save in a new Part 4 folder as Lesson2_Part4.mxd.

Add only the three natural-looking false color Landsat Look images to Lesson2_Part4.mxd, and zoom to the extent of these scenes. Note the following:

o The Landsat images are georeferenced in WGS84 UTM Zone 18, which is not the same as our data frame map projection. Allow Arc to reproject on the fly, accepting the default datum transformation.

o A single Landsat scene covers quite a large area – far larger than most counties in the US, but much smaller than most states.




o Landsat scenes are skewed with respect to the native map projection, so there are large areas of black (background) cells used to fill in the rectangular raster file.

o The Landsat 7 scene contains black stripes through all but the center of the image. These are the SLC gaps caused by a failure in the sensor system in 2003. You can read more about SLC gaps in Campbell (Chapter 6, page 179). Algorithms for gap filling involve creating masks to cover the void pixels and filling by interpolation. Depending on the application, gap-filled data may not be suitable for analysis.

o On the USGS site describing Landsat Look imagery, it explains how the 3-band Landsat Look images were created. If you were downloading the full Level 1 scene, you would have to create a correspondence of wavelength band to color gun manually when importing the scene. This is explained further in the video Accessing Landsat Imagery & Working with it in ARCGIS.

Reorder the remaining layers as follows:

o CentreCountryBoundary

o PAMAPOrthophotos

o Landsat 7

o Landsat 8

o Landsat 5

Zoom in to the area around Centre County, PA. By sheer luck, our area of interest on the Penn State Campus falls in the area unaffected by the Landsat 7 SLC gaps. We can use raster clipping tools to isolate our area of interest. getting grid of the SLC gaps as well as the large black void areas around each scene.

Add AOIBoundary.shp from the Lesson2 Part3 folder. This boundary defines our study area.

o Make the study area boundary hollow (no fill) with a 2.0 point Mars Red outline

o Move the study area boundary to the top of the TOC.

Open ArcToolbox

Use the Clip tool under Data Management→Raster→Raster Processing to clip each raster to the extent of the AOIBoundary.shp file. Save the output rasters in the Landsat folder as follows. Be sure to explicitly add the .img extension to the output file name to get the correct output file format.

o Landsat7.img

o Landsat8.img

o Landsat5.img

Zoom in to the extent of the study area (AOIBoundary) and examine the three images.

Note that the clipped result is still slightly skewed compared to the AOI Boundary polygon. This is because the files themselves are not in same map projection. For now, we won’t be concerned with that, but this is something to bear in mind when you clip data.



http://www.uvm.edu/%7Ejoneildu/Video/GIS_Open/LandsatArcGIS/Landsat%20ArcGIS.html


Q27: What is the ground sample distance (GSD) of a single pixel in the Landsat Look imagery? (1 point)

A. 1 foot

B. 1 meter

C. 5 feet

D. 5 meters

E. 30 feet

F. 30 meters

Notice that, although the USGS calls these Landsat Look images “natural color,” the colors are not “true” or “natural” as it has been defined in the reading. Why is that?

Q28: The “natural color” Landsat Look images are not “true RGB” color because:

A. Brightness values in the image file were altered by the ZIP compression

B. The USGS did not use the red, green, blue color bands to create these “natural color” images.

C. The low spatial resolution (large GSD/pixel size) causes blurring of the colors in the landscape.

D. ArcGIS mismatched the color bands in the image files with the RGB layers in the image symbology table.


Data Visualization Using the data you already have, you are going to create two shaded relief visualizations: one low resolution using Landsat and a USGS DEM, and one high resolution using orthophotos and lidar.

Remove all data from your ArcMap document except:

o CentreCountyBoundary

o LC08_L1TP_016032_20131021_20170308_01_T1.tif (the original Landsat 8 Look image)

o centretopo100.img

o PAMAP Orthophoto Mosaic

o PAMAP_Lidar.lasd

Order the datasets in the TOC as listed above.


The USGS DEM and Landsat Look images have very different extents. To make a nicer visualization, you are going to clip the Landsat Look image to the Centre County boundary. Before clipping, you should reproject the Landsat Look raster into the same coordinate system as the clipping boundary to avoid edge issues.

In ArcToolbox, under Data Management→Projections and Transformations→Raster, open the Project Raster tool.

Use the following settings to create a new version of the Landsat Look image in the desired coordinate system.

o Input Raster: LC08_L1TP_016032_20131021_20170308_01_T1.tif

o Output Raster Dataset: Landsat8_SPMeters.img



https://en.wikipedia.org/wiki/Ground_sample_distance


Be sure to save in the Lesson2_Part 4 folder

Be sure to specify the .img file format

o Output Coordinate System: NAD_1983_StatePlane_Pennsylvania_North_FIPS_3701 (Meters)

o Use the default Geographic Transformation from WGS84 to NAD-1983

Now clip the projected Landsat Look image using the Centre County Boundary. Save the clipped image as Landsat8_Clipped.img in the Lesson2_Part4 folder.

The image gets clipped to a minimum bounding rectangle around the irregular polygon boundary. To limit the display for our visualization to the area common to both datasets, you can use additional clipping options in the Data Frame Properties.

Open the Data Frame Properties and select the Data Frame tab.

Under Clip Options, select Clip to Shape and specify the outline of CentreCountyBoundary as the clipping extent.

In the first clipping operation above, you created a new image file with limited extent. In the second clipping operation, you did not change the image file, you only limited what ArcGIS is displaying in the map frame by using the Centre Country Boundary as a mask.

Create a hillshade from the USGS DEM using default settings for Azimuth and Altitude. The hillshade tool is located in the Spatial Analyst toolset. Save it as USGSDEM_Hillshade.img in the Lesson2_Part4 folder.

Turn off all data layers in the TOC, except the new USGS DEM Hillshade and the clipped Landsat 8 image.

Move the hillshade to the top of the TOC, above the Landsat 8 image and make it 50% transparent. You can set transparency the Layer Properties or with the Effects toolbar.

Zoom to the extent of the Centre County Boundary.

Q29: Create a screen shot of the shaded relief Landsat 8 image, including the map display and the ArcMap TOC. Upload it as the response to this question. Limit the width of your image to 800 pixels when inserting in the response box. (1 point)




Creating a hillshade from the lidar data is a bit more complicated, because the lidar data is a point cloud, not a raster DEM. You can learn more about using lidar point cloud data in the ESRI VC course, Managing Lidar Data Using LAS Datasets. For now, follow the specific steps below.

Return the data frame view extent to the default (no clipping) condition.

Turn off the Landsat 8 and USGS DEM datasets in the TOC.

In ArcToolbox, find the Make LAS Dataset Layer tool under Data Management→Layers and Table Views.

o Select PAMAP_Lidar.lasd as the Input LAS Dataset.

o Call the Output Layer PAMAP_Lidar_Ground.

o Check the boxes for Class Codes 2 and 8 only.

o Do not check any boxes under Return Values

Click OK, and wait a minute for the new layer to appear in the ArcMap TOC. Note if you zoom in that the layer contains lidar points, but only those classified as ground.

To create a ground (bare-earth) raster DEM from the lidar layer, find the LAS Dataset to Raster tool in ArcToolbox under Conversion Tools→To Raster.

o Select PAMAP_Lidar_Ground as the Input LAS Dataset.

o Call the Output Raster LIdarGroundDEM.img.

o Leave all other setting as default.

Now create a hillshade called LidarGroundHillshade.img using the Lidar Ground DEM.

Using the same approach as before, create a shaded relief visualization using the PAMAP Orthophoto mosaic and the lidar-derived hillshade.

Zoom to the extent of the PAMAP data layers.

Q30: Create a screen shot of the high-resolution shaded relief visualization, including the map display and the ArcMap TOC. Upload it as the response to this question. Limit the width of your image to 800 pixels when inserting in the response box. (1 point)




Documents

Developing a Project Base Map in ArcGIS · Developing a Project Base Map in ArcGIS ... Geog 480: Exploring Imagery and Elevation Data in GIS Applications ... on FTP servers, the file