ArcMap 8.x and 9.x Planetary Projection Tutorial
ArcMap 9.x now ships with Solar System definitions in the package . If you are still using ArcMap 8.3, it is still possible to set planetary projections manually without writing any scripts. Below, we will discuss below some of the questions that can still arise.
- ArcMap can project vector files to any projection on-the-fly from any other projection.
- In order to project your vector or feature files to images, it is best that all images are projected to a single projection using the appropriate parameters (center longitude, center latitude, parallels,...) and be in a GIS ready image format (ie. Geotiff and other image with a world file). See the FAQ for more image information.
- While ArcMap may have some capabilities to project raster files on-the-fly, it is best that all the images are pre-projected to the same projection. If the image projection is different from the projection you set on the data frame in ArcMap, the vector files will not be properly located on the image.
- Use the geodesic measurement tool
for measuring distances in a geographic projection or in a projection
where there are potentially large errors. ArcMap
8.x and 9.x geodesic measurement tool. In ArcMap 9.x this feature is built-in and is accessed when using the measure tool while holdin ght eshift key down.
- To report latitude and longitudes in a projection use the ArcMap 8.x or 9.x Lat/Lon display. This function is also built-in and can be enabled under the data frame's general tab.
- ALL vector files should have a projection
- When loading a vector file (shapefiles, coverages, geodatabases, ect) and ArcMap warns the user stating "missing spatial reference..." the file should be removed and a projection should be defined before re-adding the file back in. The Grid and TIN formats should also have a projection set. Regular images (bil, tif, ect) don't necessarily need them. As stated above, to fit vector files onto an image, the projection which defines the image needs to be set in the ArcMap data frame. Thus the Sinusoidal images and the Lambert images will not fit together.
- How to set a projection while creating a new
- Files should be created within ArcCatalog. When you generate a new file (i.e.. shapefile) in ArcCatalog it doesn't force you to define a projection but you should. Files without a projection (prj) file may wrongly default to an Earth coordinate system. I recommend to just define the projection using the geographic parameters. This means the features will be stored using decimal degree (lat/lon) coordinate system, but you can still use the file in any projection. If you define that the file has a projection (i.e. Mercator), you can still work in any other projection, but the coordinates will saved in in meters using the defined parameters in a Mercator coordinate system. The steps to do this include:
- How to set a projection on existing files
- To define projections on your existing files use ArcToolBox and choose "Define Projection" under "Data Management Tools" and "Projections". After selecting all your existing shapefiles which currently register together (you can keep adding to the list from multiple directories too), it is easiest to "select..." or "import..." the projection settings from an existing projection file (same as step 3 above). To manually define a projection for all your existing shapefiles use step 4a or 4b above.
- Setting a planetary projection in ArcMap
- ArcMap can have multiple data frames and each one can have a target projection. If your data frame has imagery layers (i.e. Tiffs, Jpegs, Bils) then the data frame ideally should be set to the same projection as the images. If your vector files have a projection correctly set, these files will project on-the-fly to overlay the imagery. Remember to set the geographic properties too (step 4a). To get to these dialogs right click on the data frame you wish to set and click on "properties" . This will open the data frame properties window, go to the "Coordinate System" tab, and then choose "import" to define from an existing projection file or "new" to manually enter the projection. Setting the projection for a data frame uses the same dialog window as shown in step 4b above. Once defined, it is useful, before leaving the properties window, to add this projection to your "Favorites". Next time you wish to set this projection in a new data frame you can quickly define it from your list of favorites. This is why it is a good idea or the projection to have a descriptive name.
- Predefined ArcMap 8.x Projection files for
download (use your browser's - "save as" function )
- Update July, 2004. Remove old directory if previously installed. Get the new ones above. ArcMap version 9.x comes with these files installed so you do not need them. However, for Mars, you may still need "Mars 2000 Sphere.prj" projection file.
- For Mars, the "Mars 2000 Sphere.prj" should be used for all Equidistant Cylindrical and Sinusoidal maps if the images are generated in ISIS. This is because ISIS only supports a sphere equation for these two projections.
- I have found it easiest to install all the planetary geographic definitions into the "Geographic Coordinate Systems" directory found where ArcGIS was installed. i.e. "D:\arcgis\arcexe83\Coordinate Systems\Geographic Coordinate Systems\". Place the directory "Solar System" from the zip file at that location. It now should be easily accessible from within ArcMap.
- Hint: to install to your ArcMap coordinate system "Favorites" list, copy your favorite *.prjs to your users ArcMap Coordinate Systems directory (.i.e. C:\Documents and Settings\*user*\Application Data\ESRI\ArcMap\Coordinate Systems\ -- where *user* is your Windows login name).
- All "2000" geographic values are defined from the IAU/IAG 2000 paper.
ArcMap Planetary Projection Examples (rename to *.prj)
|Planets||Geographic||Projection Example 1||Projection Example 2|
|Jupiter 2000||Jupiter 2000.prj|
|Mars 2000||Mars 2000.prj||Mars2000_Equidistant_Cylindrical.prj (for geographic w/ clon=0)||Mars2000_Equidistant_Cylindrical_Sphere.prj (for geocentric w/ clon=0)|
|Mars 2000 Sphere||Mars 2000 Sphere.prj||Mars2000_semi-minorSphere_npole.prj||Mars2000_semi-minorSphere_spole.prj|
|Mars 1979 (MDIM1)||Mars 1979.prj|
|Mercury 2000||Mercury 2000.prj|
|Moon 2000||Moon 2000.prj||Moon2000_Mercator180.prj (clon=180)|
|Neptune 2000||Neptune 2000.prj|
|Pluto 2000||Pluto 2000.prj|
|Saturn 2000||Saturn 2000.prj|
|Uranus 2000||Uranus 2000.prj|
|Venus 2000||Venus 2000.prj|
|Venus 1985||Venus 1985.prj||Venus1985_v14_
|For geographic projection files for all gathered planets and moons||
get them all here =>
|remove old directory if previously installed.|