Map Projection Using ArcGIS - CEProfs · PDF fileTexas A&M University Department of Civil Engineering 2 Brief Overview of Map Projection Using ArcGIS . Map projection involves transforming

Texas A&M University

Department of Civil Engineering

Map Projection Using ArcGIS

Francisco Olivera, Ph.D., P.E. Srikanth Koka Lauren Walker

Aishwarya Vijaykumar Keri Clary

Department of Civil Engineering Texas A&M University

April 21, 2014

Contents Brief Overview of Map Projection Using ArcGIS ............................................................................. 2

Goals of the Exercise ....................................................................................................................... 2

Computer and Data Requirements ................................................................................................. 2

Procedure ........................................................................................................................................ 2

1. Projections of the World ..................................................................................................... 2

A. View of the world in geographic coordinates (longitude and latitude) .......................... 2

B. View of the world in Robinson Projection ....................................................................... 4

C. View of the world “from space” ...................................................................................... 6

2. Projections of the United States.......................................................................................... 7

A. View of the United States in geographic coordinates ..................................................... 7

B. View of the United States in Albers Equal Area projection ............................................. 8

3. Projections of Texas............................................................................................................. 9

A. View of Texas in geographic coordinates ........................................................................ 9

B. View of Texas in Lambert Conformal Conic projection ................................................. 11

C. View of Texas in the Texas Centric Mapping System (TSMS) ........................................ 13

4. Defining the Projection ...................................................................................................... 15

5. Projecting Data Using ArcToolBox ..................................................................................... 17

Texas A&M University Department of Civil Engineering 2

Brief Overview of Map Projection Using ArcGIS Map projection involves transforming spatial data defined on the curved surface of the earth to the flat surface of a map. A map projection is the mathematical algorithm used for this transformation. ArcToolBox allows the transformation of data from one map projection to another.

Goals of the Exercise This exercise will introduce you to the procedure for projecting GIS data in ArcGIS.

Computer and Data Requirements This exercise has been completed using ArcGIS 10.2. All the data needed for this exercise are contained in the MapProj.mdb geodatabase. Download the MapProj.zip file containing the geodatabase from the class website. Unzip it and save the files to a working directory in your computer.

Procedure

1. Projections of the World

A. View of the world in geographic coordinates (longitude and latitude) (1) Open a new ArcMap document. Add data to your map, using the Add Data button

and browse to the MapProj.mdb geodatabase in your working directory. (2) Double click on the geodatabase to access the feature classes inside it. Select the

cntry94 and world30 feature classes while holding down the Ctrl key, and then click Add. Make sure that world30 is below cntry94 in the Table of Contents.

(3) To show just the outlines of the features in the world30 layer, click on the symbol for

world30 in the Table of Contents. On the left hand side of the Symbol Selector window that opens, you can see a list of color schemes; select the one named Hollow, and then click OK. You can now see the world map in geographic coordinates.


(4) To label the countries, right-click on the cntry94 layer and select the Label Features option in the dropdown menu. To customize the label display, right click on the layer, and then click on Properties/Labels. To remove the labels, unselect the Label Features in this layer option and click OK.

(5) To label a few selected countries, first display the Draw toolbar in ArcMap. Click on Customize/Toolbars/Draw to add it to the map.

(6) On the Draw toolbar, click the down-arrow beside the New Text button , and

select the Label option . (7) In the Label Tool Options, choose the Placement and Label Style of your preference

and close the form. Click on the countries you want to label. Save the project as World.mxd.


Move the cursor around on the view and you will see a pair of numbers to the bottom right of the ArcMap window. These numbers are the coordinates of the cursor and from the values displayed in the bottom right part of the screen you can see that they are displayed in the degrees minutes format in decimal degrees and are the latitude and longitude of the cursor location.

B. View of the world in Robinson Projection

The map projections of cntry94 and world30 are geographic; however, they can be viewed in different projection systems. A common projection system for the world is the Robinson projection. (1) Create a new data frame in ArcMap using Insert/Data Frame. Add the world30 and

cntry94 feature classes to this new data frame by right-clicking on New Data Frame and selecting Add Data or from the File dropdown menu.

(2) Again, rearrange the layers and change the legend of world30 as explained in the

previous section. To view the world in Robinson projection, right click on the new data frame and click on Properties/Coordinate System.

(3) In the Select a Coordinate System box, click on Projected Coordinate

System/World/Robinson (World) and then click OK.


(4) Click Yes on the warning message that appears. You will see the world in the Robinson

projection. Refresh the map by clicking on the Full Extent tool , and then save the document.

The Robinson projection is a world map projection designed to present the whole earth with minimum distortion at any location. If you move the cursor over this space, you should see that the coordinates are now in meters instead of decimal degrees in the projected coordinate system. (NOTE: If your coordinates are still displayed as degree minutes or decimal degrees, you can change them to meters by right clicking the New Data Frame and selecting Properties/General. Select Meters in the Display scroll-down menu in the Units box.)


C. View of the world “from space”

(1) Create a new data frame and add the world30 and cntry94 feature classes to it. Again, rearrange the layers and change the symbol color if necessary.

(2) To view the world “from space,” change the data frame coordinate system to

Projected Coordinate System/World/The World from the Space and select OK. As before, a warning message appears where you should select Yes. Refresh the map by clicking on the Full Extent tool, and then save the document.


2. Projections of the United States

A. View of the United States in geographic coordinates

(1) Create a New Empty Map file and save it as USA.mxd. (2) Add the states and latlong feature classes to the data frame. These data are polygons

of the states of the United States and lines forming a 5-degree grid of latitude and longitude.

(3) Click on the Zoom In tool and zoom into the contiguous United States. If

necessary, use the Pan tool to move the map to the center of the window.


B. View of the United States in Albers Equal Area projection

The Albers Equal Area projection has the property that the area bounded by any pair of parallels and meridians is exactly reproduced. While the projection preserves the correct area, it somewhat distorts the direction, distance and shape. (1) Insert a new data frame and add states and latlong. Zoom into the contiguous United

States. (2) To view the United States in Albers Equal Area projection, right-click on the data frame

and click on Properties/Coordinate System. In the Select a coordinate system box, click on Projected Coordinate System/Continental/North America/USA_Contiguous_Albers_Equal_Area_Conic and click OK. Choose Yes if a warning box appears. Save your document.

Zoom in and compare the shape of the United States in geographic coordinates and in Albers projection. You can see that in geographic coordinates the United States appears to be wider and flatter than it does in Albers Equal-Area Projection. This effect occurs because as you go northward, the meridians converge toward one another while the successive parallels remain parallel to one another. When you reach the North Pole, the meridians converge completely.


In Albers projection, the square boxes of latitude-longitude appear as elongated quadrilaterals with a bottom edge longer than their top edge. In geographic coordinates, the effect of the real convergence of the meridians is lost because the latitude and longitude grid form a set of perpendicular lines, which is what makes the United States seem wider and flatter in geographic coordinates.

3. Projections of Texas

A. View of Texas in geographic coordinates

(1) Create a New Empty Map file and save it as Texas.mxd. (2) Add the counties and latlong feature classes to the data frame, and rearrange the

layers and change the symbol colors if necessary.

Since we are concerned only about Texas, it is only necessary to make the Texas counties visible. (3) Right click on the Counties layer and then click on Properties/Symbology. In the Show

box, click on Categories/Unique Values. In the Value Field box, select STATE_NAME.


(4) Click the Add Values button. Click on Complete List. Then, click on Texas, the Add to List button, and then on OK. Uncheck the <all other values> box. Click Ok.

(5) Zoom into the Texas part using the Zoom In tool. The latitude and longitude grid displayed is at 5-degree intervals. You can determine what latitude or longitude a particular line represents by moving the cursor to any line and read its value on the right corner of the tool bar.


B. View of Texas in Lambert Conformal Conic projection

The Lambert Conformal Conic projection is a standard projection for presenting maps of land areas whose East-West extent is large compared with their North-South extent. This projection is “conformal” in the sense that lines of latitude and longitude, which are perpendicular to one another on the earth’s surface, are also perpendicular to one another in the projected domain. (1) Insert a new data frame and add counties and latlong data. Follow previous directions

to select to view only Texas. (2) To view Texas in Lambert Conformal Conic projection, right-click on the data frame

and click on Properties/Coordinate system. In Select Coordinate System box, click on Projected Coordinate System/ Continental/ North America/USA_Contiguous_Lambert_Conformal_Conic, then OK.

If necessary, select Yes in the warning message box. After clicking the Full Extent button, it can be seen that the meridians converge to a point. Make sure that you are only viewing Texas counties by following the steps that were outlined previously in Part A.


After zooming in to Texas with the Zoom-In tool, a more familiar shape of Texas can be seen.

Notice that Texas appears to be tilted to the right slightly. This occurs because the Central Meridian of the projection used is 96ºW, which would appear as a vertical line in the display


if it were shown. Regions to the west of this meridian (most of Texas) appear tilted to the right while those to the east of this meridian appear tilted to the left. C. View of Texas in the Texas Centric Mapping System (TSMS)

In order to present a more pleasing map of Texas, and to minimize distortion of distance in statewide maps, the Texas Department of Information Resources has approved two standard projections of Texas called Texas Centric Mapping System (TSMS) (http://www.dir.state.tx.us/tgic/committee/stnd/draft-rule-2001.pdf). One of them is Albers Equal Area and the other Lambert Conformal Conic. Their definition is: Projection: Albers Equal Area (or Lambert Conformal Conic) Datum: North American Datum of 1983 (NAD83) Ellipsoid: Geodetic Reference System of 1980 (GRS80) Map units: meters Central Meridian: 100°W (-100.0000) Reference Latitude: 18° N (18.000000) Standard Parallel 1: 27° 30' N (27.500000) Standard Parallel 2: 35° N (35.000000) False Easting: 1500000 False Northing: 6000000 (or 5000000 for Albers Equal Area) This means that the standard parallels, where the cone cuts the earth's surface, are located at about 1/6 of the distance from the top and bottom of the State, respectively, and that the origin of the coordinate system (at the intersection of the Central Meridian and the Reference Latitude) is in the center of the State, to which the coordinates (x, y) = (1500000, 6000000) meters is assigned, so that the (x, y) coordinates of all locations in the State are positive.

(1) Insert a new data frame and add counties and latlong layers as done previously. (2) Right-click on the data frame and click on Properties/Coordinate system. In the Select

Coordinate System box, click on Custom. Click on Add Coordinate System button and then on New/Projected Coordinate System button.

(3) Enter the map projection information given above as shown below. In the Geographic

Coordinate System box, click Change and in the Spatial Reference Properties window click on North America/North American Datum 1983.prj/Add. Then click OK button to finish projecting the data frame.


Zoom into the Texas part using Zoom In tool. (Make sure you are only viewing Texas counties by following the steps in Part A.)


4. Defining the Projection Every dataset is either in a geographic coordinate system or in a projected coordinate system. ArcMap cannot determine what projection a dataset is in unless and until it is specified. For shapefiles, this information is stored in a file with extension prj. Geodatabases store it as a table within the database. Even though a dataset might have a coordinate system, the corresponding projection information might be missing. In this case, the information has to be obtained from the data source and the projection should be defined. If you add a layer to a data frame and its projection information is missing, you will get the following message:

This is not a problem for displaying data as long as ArcMap does not need to project it on-the-fly. In this part of the exercise, you are going to define the projection information of the STATSGO (State soil geographic dataset) data of Texas. This dataset contains soils information for the state of Texas, but its spatial reference properties are not defined. So, the information has to be obtained from the host of the data. The dataset was obtained from the United States Department of Agriculture (USDA).

(1) Before defining the projection, open a new ArcMap document, and add quad and STATSGO to the data frame. You will see the above-mentioned warning message and you will observe that both the layers do not overlay upon one another. This is because ArcMap does not know the projection details of STATSGO.

(2) Close the document because you cannot define the projection of STATSGO in

ArcCatalog if ArcMap is using it.


Listed below are the values that will be used to define the projection. Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Albers_Conical_Equal_Area: Standard_Parallel: 29.50 Standard_Parallel: 45.50 Longitude_of_Central_Meridian: -96.0 Latitude_of_Projection_Origin: 23.0 False_Easting: 0.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 6.35 Ordinate_Resolution: 6.35 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 294.9786982

Though projection for datasets can be defined either with ArcCatalog or ArcToolBox, we will use ArcCatalog in this exercise.

(3) In ArcCatalog, browse down to the geodatabase, open the geodatabase, right-click on the STATSGO feature class and then click on Properties.

(4) In the Feature Class Properties wizard that opens, click on the XY Coordinate System

tab. You can see here that the XY Coordinate System for this feature class is ‘unknown’.

(5) Double-click on Projected Coordinate Systems/Continental/North America/ USA

Contiguous Albers Equal Area Conic USGS. (6) Click Apply and then click OK.


(7) Again, open a new ArcMap document and add the Quad and STATSGO layers. This time you should not see the warning message and you will see the layers overlay one upon another.

(8) To clearly see the layers, make sure that the first layer is STATSGO and the second is

quad. Change the symbol color of STATSGO and make it transparent (hollow). (9) Do this by clicking on the square below the layer name and then select Hollow in the

Symbol Selector Wizard. Your map should look similar to the image below.

5. Projecting Data Using ArcToolBox Data in one projection can be transformed into another projection. It is very useful for all the data layers to be one projection when they refer to the same spatial extent.

(1) Before going on to changing the projection of STATSGO, in ArcMap start ArcToolBox

by clicking on the red toolbox icon on the toolbar. (2) Click on Data Management Tools/Projections and Transformations: Click on

Feature/Project.


(3) Click on the folder icon located to the right of the Input Dataset or Feature Class.

Browse to the folder where MapProj.mdb is located. Double-click on the geodatabase to see all the feature classes inside it.

(4) Select the STATSGO feature class and click on the Add button to choose the feature

class that is to be projected. (5) Select the folder icon to the right of Output Coordinate System. Double-click on

Projected Coordinate Systems/Continental/North America/USA Contiguous Lambert Conformal Conic, and click OK twice. The program will begin to execute the projection.

(6) To verify if the dataset is projected properly or not, open a new ArcMap document and

add quad and STATSGO_Lambert to its data frame. If it has been projected properly, then they should overlap.


One more thing that should be noted is the capability of ArcMap to project data on-the-fly. Try to see the spatial reference properties of the two layers in the map by right-clicking on each of them and then clicking on the Properties, then on Source tab in the Layer properties wizard.

These materials may be used for research and educational purposes only. Please credit the

authors and the Department of Civil Engineering, Texas A&M University. All commercial rights reserved. Copyright 2014: Texas A&M University.

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Map Projection Using ArcGIS - CEProfs · PDF fileTexas A&M University Department of Civil Engineering 2 Brief Overview of Map Projection Using ArcGIS . Map projection involves transforming