Map Projections Tips

Map Software

• I have developed a number of map projection routines that I use in IDL.

Map Examples

• You can find a number of examples of IDL graphics output using map projections in the Coyote Plot Gallery.

Map Projections and Images

• How do I add an 8-bit image to a map projection?
• How do I add a 24-bit image to a map projection?
• How can I georeference an image I downloaded from the Internet?
• How do I display a satellite image on a map projection?
• Can I associate a map coordinate system with an image that is already in a map projection?
• Can you show me how to navigate a GOES image?
• I am having trouble navigating an NSIDC ice shelf image. Can you help me?
• Can you show me how warp an image from one map projection to another in IDL?
• Can you show me how to display a gridded land cover image on a map projection in IDL?
• Can I display a Google map in an IDL graphics window?
• Does the IDL 8.2 Map function work with gridded images?
• Is the LIMIT keyword to the IDL 8.2 Map function screwy?
• How can I display data with associated longitude and latitude values on a map?
• How can I extract a portion of an image based on map coordinates?
• Yikes! Why is my image clipped when displayed on a map projection?

Working with GeoTiff Files

• Can you show me how to overlay geographic information on a GeoTIFF image?
• Can you show me how to annotate a GeoTiff image?
• Can you show me how to extract latitude/longitude values for each pixel in a GeoTIFF image?
• How can I open a GeoTIFF image and have it automatically be georegistered?
• Can you show me how to navigate a GOES East or West GeoTiff image?
• How can I find the image pixel location of a specific latitude and longitude in a GeoTiff file?

General Map Projection Tips

• How do I contour irregular data on a map projection?
• How come !P.Multi doesn't work with map projections?
• Aaauuugh! How can I center a map projection over the Pacific ocean?
• The colors on my filled contour map projection are completely wrong. What's going on?
• How do I convert normal longitude values (-180 to 180) to values ranging from 0 to 360?
• Can you show me how to draw a map with a day/night terminator shown?
• Be careful using Map_Proj_Init with GCTP map projections.
• How can I match point source data with gridded maps?
• Can you show me how to convert UTM coordinates to latitude/longitude?
• Isn't there a simple method to convert between UTM and lat/lon coordinates?
• Can you show me how to grid data into a map projected study area?
• “Choose wisely when choosing Mercator (or any other) map projection.”
• How can I fake a cylindrical equal-area map projection in IDL?
• Whoa! Did my GCTP map structure just change on me?
• Why can't I set a latitude of true scale in my polar stereographic map projection?
• Can you help me create a GPD file to use in gridding satellite data?
• How can I get rid of this gap in my filled contour plot on a map projection?
• The UTM map projection produces incorrect results with WGS84 datum.
• Alber's Equal Area silent substitution affects map projection results.
• The Map function knows no bounds in IDL 8.1.
• Does Map_Proj_Init calculate incorrect UV ranges?
• New Coyote Graphics map projection routines are now available!
• Can you show me how to browse and visualize an HDF-EOS grid file?
• Compare filled contour plots on maps in different graphics systems.
• Can you show me how to create polar wind vector plots?

Adding Map Annotations

• My contours extend over the ocean. How can I mask these sea contours out of my map projection?
• Are there better options for continental outlines on maps than the built-in database?
• How can I query and display map information on a map-projected image?
• “I just want to overlay this map boundary on a MODIS image,” she purred.
• How do you set up a map coordinate space so you can draw map boundaries and grids on an image?
• Can you show me how to overlay geographic information on a GeoTIFF image?
• Can you show me how to annotate a GeoTiff image?
• Can you show me how to overlay point source data on a map?
• Yikes! Map_Grid doesn't clip map labels if I use hardware or true-type fonts!
• What does Map_Continents have against the NE United States that it won't draw them?
• Portions of my map grid lines are missing. Why?
• Where do the extraneous lines in Map_Grid come from?

Working with Shapefiles

• How can I use my own political boundary database (shapefiles) on map projections?
• The shapefile I made from CONTOUR doesn't quite line up on my map projection. Why not?
• My shapefile programs take forever to run! What am I doing wrong?
• Yikes! My shapefile is going berserk!
• How can I browse the content of my shapefile?
• Is there a way I can draw the shapes in my shapefile?
• How can I extract a polygon from a shapefile?
• How can I display transparent polygon shapes on a map?