Wednesday, December 8, 2010

Alaska Map "Painting"

Some of you may already know this, but I make maps. I took the opportunity to make a custom map for my dear friend who spent some time doing mountaineering school in Alaska. I figured, I have the knowledge, power and skill to pull this off. So I set out to create a topographic map of the area he spent time in. Here it is, and I'll explain my methodologies as well if you are interested.

Matanuska Glacier and Powell Glacier
(original size= 24"x36") sorry if it's too small the see here
First, I visited the USGS website and selected the seamless server NED (National Elevation Data) download page. I zoomed into the area that I needed and selected the area with the download cursor. The 1" NED data wasn't available for that region and neither was the 1/3" or the 1/9" so I was forced to settle with the 2" NED Data. Instead of giving me a seamless raster, it brought back 4 tiles for my selected region. I downloaded the tiles (4) and extracted them all to my project folder.

Then I added all 4 rasters to my ArcMap document and projected the entire data frame as "State Plane 83 Feet Alaska FIPS 3" It projected the data quite nicely. I then went into the toolbox to merge the 4 tiles to make them seamless. This is called mosaicing, it "stiches" the images together making them one. It seemed that I had to make a raster in as the output, so I just went into ArcCatalog, copied one of the raster folders that I extracted and gave it a new name, "Output." Then I went back into my ArcMap document and hit the "Mosaic" tool in the ArcToolbox. I navigated to my newly created raster as my output and added the four rasters to the list of desired tiles. I gave it a name "merge" and hit ok. After a couple minutes it was done mosaicing (praise the programming gods) and the image was complete. The 4 tiles were now one raster. I saved the .mxd (Esri map document) as chugach.mxd as this is the area of interest. I will begin beautification.

Creating the hillshade was fun and ridiculous at the same time. I tried 15 different combinations of azimuth and altitude before I settled on one that I liked. I found that, at least in this case, staying close to the default was the best choice. The purple color represents the highest elevations which melt into brown, yellow, green and then finally blue being the glaciers.

The contour lines were a whole separate ballpark. I created them using Spatial Analyst (pretty solid ArcGIS tool). I took the DEM (Digital Elevation Model) and, since I had merged 4 tiles together, had to adjust the range values. Excuse me if I'm being brief/vague with my methodology. This isn't meant to be a tutorial. Then I created the contour lines, I had to convert my values from meters to feet, which was also a series of trial and error, but I finally got it. I am displaying only the contour lines with easily readable values (2000, 3000 etc.) at intervals of 20 feet. I then labeled only the primary contour lines and gave them a more prominent line weight/color. The secondary contour lines are displayed but not labeled, but since they are at every 20 feet, you can deduce what the value of that line actually is.

I also set out to make it so sweet, but unfortunately there wasn't too much available data for what I was looking for. I found some really excellent sources of data that seemed to be good leads until I downloaded them and tried using them. For example, I wasn't able to find a complete point dataset with the peaks and their common names of the area. It would be really cool if someone who is really familiar with the area created a dataset like that. I found some great glacier data that I also used in the map. Anyway, since my resources were limited to internet database searches, I decided to make it look more like a painting than an actual "navigational" map. Enjoy!


  1. You make it sound easy! Great map Kelly!

  2. You're a nerd!And I'm so proud to be your Mom!

  3. Oh yeah...I fully understand how you put this map together...especially with the azimuths, rastar folders, and mosaicing tiles! Better you than me! Ha-ha