Technical Details

This pages describes the procedure that was used to generate the bathymetric maps.

It all started with a set of Excel files that contained the measurements (reduced data) made by Richard Ortt of DNR over a seven day period in April of 2012. There were over 600,000 records of measurements.

We did some sanity checks with the data with Excel and after several email exchanges we discarded several hundred data records that were clearly bad, a very small amount considering.

One of us decided that the "R" language was to be learned for its graphics features and computational capability in order to process and display the various kinds of data. This turned out to be a major commitment, lasting four months to get to the ability to produce the graphs that are on this website. R has a very steep learning curve, but is very powerful and quite flexible.

The was time well spent.

To make the bathymetric maps and superimpose the boatslips on them required the following:

1. An outline of the the boundary of the lake. We obtained that from Debbie Carpenter, Garrett County Department of Planning and Zoning, in the form of an ESRI shape file.
2. A list of the locatons of the boat slips. One of us digitized the boat slips (3,377) using Google Earth from an image dated 7/9/2011, the middle of the boating season. Google Earth turned out to be remarkably accurate.
3. Software (R has many "packages" to choose from; it was often not clear which one to go with) to process the irregularly spaced data points into regular data and from them create the depth contours and color coding system.
4. Conversion of data from lat/lon (as acquired by the gps system) to the Maryland State Plane Coordinate System because the lake outline was in those coordinates.
5. Write and test the software and produce the maps

The whole process took about four months.