Bathymetric Maps of Deep Creek Lake

by on under Bathymetry
5 minute read

Analysis

The bathymetry of Deep Creek Lake1, as can be found on the deepcreekanswers.com website, consists of many maps, for two reasons:

  1. The software I used, “R”, cannot2 do the whole lake at the resolution that I desire, namely 10 ft. This has to do with R being able to generally run in memory only, and the matrix manipulations required for the whole lake at the desired resolution requires too much RAM, more than the 12 Gb that I have already.
  2. A large map cannot contain the level of detail that small scale maps can.

The computation of contours from many irregularly spaced data points can be a difficult problem. This is not an uncommon scientific or mathematical need. As a result many algorithms have been developed, often for very special purpose applications. Think for example where weather stations are located, collecting temperatures, pressures, humidity, wind speeds and direction, rainfall, and solar radiation, all at certain time intervals, and how this information is interpolated to give values at arbitrary locations.

For our purposes, I have focussed on using the Akima3 scheme of interpolating. Over many years of working with data, I have found this algorithm to be quit reliable. The R community has not embraced this algorithm too much because the author still claims certain copyrights, which is against the philosophy of the R platform, it being open and unrestricted.

At the time this work was done, the R management group was soliciting for a software developer to write unrestricted software for this algorithm. The most recent update of the ‘akima’ software on R dates to 2015 and still contains a restricted license for using it. Fortunately, this does not matter for our purposes because we’re using it for a research application and not for financial gain.

The results on ‘deepcreekanswers.com’ were generated with the older version of the algorithm. A future note will delve into how different the revised algorithm is. It’s expected not to make much difference, given the basic uncertainties inherent in interpolating data that are irregularly spaced. There are three folders/directories containing the resulting maps:

1. Akima
2. Akima2
3. Loess

Akima is the interpolation scheme for producing the maps, while Loess is a smoothing scheme. The Akima folder contains maps in which the contours are just shown as colors. Akima2 contains, in addition, contour lines. The filename for each map encodes the name of the cove or area, the resolution of the map in ft, and the mapping scheme, for its name, either akima or Loess. Use whatever you feel comfortable with, after all they are all approximations. The mathematical and programming details will be explained in future notes, as a review and document the process. The areas for which maps exist are shown on an overall map as shown in Figure 1. One that can be enlarged and still show detail can be found on the deepcreekanswer.com website. Here are all of the areas for which I have produced bathymetric maps based on DNRs data of April 2012. They are the names for the following coves/areas:

1 Name ID
2 Anglers Cove Anglers
3 Arrowhead Cove Arrowhead
4 Blakeslee Blakeslee
5 Carmel Cove Carmel
6 Cherry Creek Cove CherryCreek
7 Dam Dam
8 Deep Creek Cove DeepCreek
9 Deep Creek Bridge DeepCreekBridge
10 East Deep Creek Bridge EastDeepCreekBridge
11 Glendale Bridge GlendaleBridge
12 Green Glade Cove GreenGlade
13 Green Glade All GreenGladeAll
14 Harveys Cove Harveys
15 Hickory Ridge HickoryRidge
16 High Mountain Sport HMS
17 Hoop Pole HoopPole
18 Lakeshore1 Lakeshore1
19 Lakeshore2 Lakeshore2
20 McHenry Cove McHenry
21 North Glade East NorthGladeEast
22 Pawn Run Cove PawnRun
23 Penn Cove Penn
24 Poland Run Poland
25 Red Run Cove RedRun
26 South Center SouthCenter
27 South West SouthWest
28 Sky Valley SkyValley
29 Turkey Neck TurkeyNeck
30 Barb’s Cove BarbsCove 4
31 Glen Cove GlenCove
32 Gravelly Run GravellyRun
33 Sandy Beach SandyBeach
34 Hazelhurst Hazelhurst

If other maps are needed just give me the longitude and latitude of the center of the area you want and a rough radius around that point and I’ll try to generate one.

You can e-mail those to: pete@deepcreekanswers.com.

Use this e-mail address also to tell me if you find any problems with any of the maps.


PLV - First Published: 5/12/2012
Revised: 3/23/2016 ID: DCL005

  1. The initial version of this note was written at the indicated date. Small editorial changes and footnotes have been added to the official record of my work. 

  2. At the time the work was done this could not be accomplished. Fortunately with a newer version of R and more memory on my computer I was eventually able to generate whole lake maps that could be printed on 3 ft x 4 ft sheets. 

  3. Hiroshi Akima, “A Method of Bivariate Interpolation and Smooth Surface Fitting for Irregularly Distributed Data Points”, ACM Transactions on Mathematical Software, Vol. 4, No. 2, June 1978, pp. 148-159. Copyright 1978, Association for Computing Machinery, Inc. 

  4. When this work was done I could not find anyone who knew the official name of this cove. It has since become to be known as “Chadderton’s Cove.” 

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