Maputo Map Creation Procedures 3 Oct 2012, Emily Eros
1. Base imagery and roadsSourcing from ESRI World Imagery base layer[footnoteRef:1]Also sourcing OpenStreetMaps[footnoteRef:2] as a (partially-transparent) overlayChecked projection of the map our base layers are projected in WGS 1984 Web Mercator, with units in metres. Im okay with that WGS 1984 is the spheroid we want to use, and the Mercator projection is good for north-south-oriented regions and areas like Mozambique. Im not sure about the web mercator part, but I know Web Mercator is required for some forms of online, interactive maps, so lets go with this.Ill be working with backup data on my USB key and we may move the data in the future, so Im going to use relative pathnames to make it easier to restore/load the map after moving data.File Map Document Properties Store Relative Pathnames (checked) [1: This map presents low-resolution imagery for the world and high-resolution imagery for the United States and other areas around the world. The map includes NASA Blue Marble: Next Generation 500m resolution imagery at small scales (above 1:1,000,000), i-cubed 15m eSAT imagery at medium-to-large scales (down to 1:70,000) for the world, and USGS 15m Landsat imagery for Antarctica. The map features i-cubed Nationwide Prime 1m or better resolution imagery for the contiguous United States, Getmapping 1m resolution imagery for Great Britain, AeroGRID 1m to 2m resolution imagery for several countries in Europe, IGN 1m resolution imagery for Spain, IGP 1m resolution imagery for Portugal, and GeoEye IKONOS 1m resolution imagery for Hawaii, parts of Alaska, and several hundred metropolitan areas around the world. Additionally, imagery contributed by the GIS User Community has been added in Alaska, New York and Virginia.i-cubed Nationwide Prime is a seamless, color mosaic of various commercial and government imagery sources, including Aerials Express 0.3 to 0.6m resolution imagery for metropolitan areas and the best available United States Department of Agriculture (USDA) National Agriculture Imagery Program (NAIP) imagery and enhanced versions of United States Geological Survey (USGS) Digital Ortho Quarter Quad (DOQQ) imagery for other areas. For more information on this map, visit us online at http://goto.arcgisonline.com/maps/World_Imagery] [2: http://www.OpenStreetMap.org.]
2. Add Mozambique data just for fun since this is a basemap and I want to see whats out there.Sourced from GeoCommunity (http://data.geocomm.com/catalog/MZ/index.html). You need an account to use this website, though most data is free.I downloaded a bunch of roads, utilities, and other transit data. They came as zip files which unzipped to a .e00 extensions. This extension is for an ArcInfo interchange file. There are some particular rules for using this data; you have to have the right sort of filename and stuff. Also, WinZip can mess with the data. If youre ever having problems, heres a link to file specs, WinZip troubleshooting, and the instructions for importing interchange files (scroll down to ArcGIS 10 instructions): http://support.esri.com/es/knowledgebase/techarticles/detail/21052Note: When converting several files at the time, you can right-click Import from E00 in the ArcToolbox menu and select Batch. That processes multiple files at once.I checked the layers and didnt like what I saw Geocomm roads didnt line up with OpenStreetMaps (which seems more reputable in this case its more locally-created and it lines up better with topography and aerial imagery). Its not a projection issue but a data-quality issue. When I try to investigate the attribute tables, ArcMap crashes. Seems suspect. Im removing and deleting the Geocomm data.
3. Downloaded elevation data for the relevant area of Mozambique (10 degree grid: 20-30S, 30-40E) from the Geocomm site[footnoteRef:3]. The DTED (Digital Terrain Elevation Data, Level 0) data comes in several grids. We need the grids for e032: s26 and s27. The rest are for other areas of Mozambique and can be deleted to conserve file space.Ive grouped and renamed the DEM layers to make them easier to work with. For the display, each DEM grid has its own scale of colours from low to high. Im going to standardize these between grids. In the Properties menu for the DEMs, Ive set a scale from 0 to 1000. 0 to 1000 of what units? Theres no metadata to answer that, but googling tells me that DTED data always supplies elevation data in metres.I overlayed the DEM data on the imagery and did a partial transparency to make sure the elevation data lined up with the land and sea, and to ensure that the two grids lined up seamlessly. Looks good. [3: Source info: http://data.geocomm.com/readme/dted/dted.htmlIn support of military applications, the National Imagery and Mapping Agency (NIMA) has developed a standard digital dataset (Digital Terrain Elevation Data (DTED) Level 0) which may be of value to scientific, technical, and other communities. This DTED product is a uniform matrix of terrain elevation values which provides basic quantitative data for systems and applications that require terrain elevation, slope, and/or surface roughness information. DTED Level 0 elevation post spacing is 30 arc second (nominally one kilometer). In addition to this discrete elevation file, a separate binary file provides the minimum, maximum, and mean elevation values computed in 30 arc second square areas (organized by one degree cell). Finally, DTED Level 0 contains the NIMA Digital Mean Elevation Data (DMED) providing minimum, maximum, and mean elevation values and standard deviation for each 15 minute by 15 minute area in a one degree cell. This initial prototype release is a "thinned" data file extracted from the NIMA DTED Level 1 holdings where available and from the elevation layer of NIMA VMAP Level 0 to complete near world wide coverage.The current DTED Level 0 and subsequent releases will be updated consistent with established NIMA production maintenace procedures. ]
4. Dowloaded 1M drainage area for Mozambique (rivers). If this is wrong, we could model it ourselves using hydrology application of ArcMap. I extracted the zipped files, imported from e00 to coverage (see ESRI instructional link above) and added the files to the map. Lines up but crashes ArcMap every time I try to check the attribute table. Thats no good. Im done with GeoComm sourced from ESRI.
5. Lets try geocoding our participatory mapping points. First Im going to clean up the database. We need all classifications to be numeric, so I added a land use code. I also split the coordinates into an X and a Y column. I saved the excel file, closed it, added it to the map, and checked the attribute table to make sure everything looked okay. Im a little nervous about geocoding WGS coordinates, but here goes. First, I changed the coordinate system of the data frame to the same as the incoming XY layers projection (GCS WGS 1984 you select this by right-clicking Layers and changing the projection). The Add XY Data option is hidden away in ArcMap 10 you have to go to File Add Data Add XY data. In the menu that appears, my data isnt showing up properly only a few columns show up. Weird. I checked out some troubleshooting strategies on ESRIs website[footnoteRef:4]. Seems like the problem is because I have coordinates in degrees-minutes-seconds and I want them in decimal degrees. Im going to convert them. I do this by running the Convert Coordinate Notation geoprocessing tool (Find it under ArcToolbox Data Management Projections and Transformations) and then performing a join to preserve other fields[footnoteRef:5]. This failed. I think this is partly because I needed to use a positive/negative denotation rather than E and S. When working with coordinate systems, we generally use the following system to denote direction: Northern: +Y Southern: -Y Western: -X Eastern: +X [4: http://support.esri.com/en/knowledgebase/techarticles/detail/39972] [5: For more info on manipulating coordinates: http://blogs.esri.com/esri/arcgis/2011/01/05/converting-and-displaying-coordinates-in-arcgis-10/]
Changing this didnt help. ESRI tells me its because degree-minute-second (DMS) coordinates are single string and must be in the format DD MM SS.ssss DDD MM SS.ssss. Latitude is first followed by longitude separated by spaces. I changed this in the input file and tried again. No luck. At this point I just did the conversion manually in Excel by splitting the degrees/mins/secs into different columns and then adding them together (Decimal degrees = (Seconds/3600) + (Minutes/60) + Degrees). I copied and pasted as values to make this GIS-compatible.
Back to the beginning were going to re-try adding the coordinates as XY Data. Success!
A few points are in suspicious locations looks like a typo in a few coordinates. Another coordinate is in a marsh. We checked the typos for this, fixed the Excel sheet, and re-imported the coordinates.
Success! The points are all showing up on the map in spots that make sense.
6. Bring in the AutoCAD files, which have been uploaded to DropBox. Normally bringing AutoCAD files in involves lots of geocoding and headachey stuff, but it looks like these have already been given spatial references and a projection, and have already been converted to GIS-compatible shapefiles. GREAT. I added all the polygons and polylines into ArcGIS just by clicking the Add Data button.The shapefiles appear in the Table of Contents. It looks like a bit of a mess and needs to be cleaned up. When converting from AutoCAD to GIS, each layer is broken into two layers one for enclosed objects (polygons) and one for not-enclosed objects (lines). I grouped together the polygon and polyline file for each layer and named them with meaningful names (water, transportation, structure, property lines, and contour lines