Thursday, April 18, 2013

BWCA Lake Contours

Awhile back I started working on adding lake contour overlays to the interactive map and the Google Earth downloads. I was using the lake map images from the Minnesota DNR Lake Finder. (Cleaning up and adding each lake is a lengthy process.) Recently I found another source of data for lake contours - the Minnesota DNR Data Deli. This service has GIS data (basically data in latitude/longitude format that can be used in mapping applications). I was able to find the lake contour data for the state of Minnesota. I downloaded the portion pertaining to the BWCA (and the surrounding area) and added it to the map.

To view the lake contours, go to the interactive map or the lake database. On the interactive map, right-click on a lake to view the options menu. If lake contours are available, you will have an option that says Show Lake Contours. Selecting this will load the data. In the lake database, a column will say if lake contours are available. The contours will load automatically when you view the individual lake page. If the lake contours are the new GIS data, the contours appear as black lines. Hovering over a line with the mouse will show you how deep it is at that spot.

Brule Lake Contours
 I have kept all of the images that I converted for use with the map because not all lakes have the new GIS data. I will continue to work on the image overlays, but the GIS data was a huge leap forward in this effort. I was able to add 74 lakes in the time it would have taken me to add 3 or 4 images. Now 123 lakes on the map have contour data.

"What about the Quetico?" you ask. Well, not many lakes in the Quetico have been mapped. A few years ago, 16 lakes were chosen randomly by the Ontario Ministry of Natural Resources to be surveyed. It does appear to be random since the lakes chosen were not necessarily popular, well-known, or even can be accessed. I know where the data is, I just don't have access to it (yet), so I can't add it to the map. However, you can view them using Ontario's Fish ON-Line map. Here is how you can use it:
  1. Go to Ontario Fish ON-Line
  2. Click on the "I agree" to get to the map
  3. Click on the search by water body name button on the left
  4. Type in Dahlin and press enter
  5. Click on the red A marker that shows up in the middle of the screen
  6. Mark the Lake Depth Contours box
  7. This should show the contours for all of the lakes that have them, not just Dahlin.
Here is the list of Quetico lakes that I know have lake contour data:
  • Badwater
  • Ballard
  • Bentpine
  • Brewer
  • Conk
  • Dahlin
  • Darkwater
  • French
  • Gratton
  • Jack
  • Little Roland
  • Lynx
  • Middle Roland
  • No Man
  • Pond
  • Pulling 
Why did it take me so long to be able to find all of this data? Well, I didn't know the technical term for lake contour data. It's bathymetry. Once I started using the right search terms, I was able to find it pretty easily.

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