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Benchmark Maps

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Good find.


Apparently well done, though at $40/state in most cases, it can get pricey if you travel a lot. I do pretty well with USAPhotoMaps and imported .GPX files, which also gives you benchmarks displayed on aerial photos.


One nice touch on the DeLorme product - what looks like different markers for horizontal and vertical control.



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Loudoun County Virginia sells a wall sized print of all NGS benchmarks in the county for $10 at the clerks office. We got ours for free as it was smudged in one corner. :D


Look like good maps though, handy for route planning. I like them in MapSource though as I use different icons for found, not found, note, and destoryed.

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Stupid newbie question: where do you get the .GPX files to import into Photomaps?

Piece o' cake. You need a program called BMGPX, which you can download from Ron Parker's "Fuzzy's Geocaching Page o' Wonders".


This very small program (zip download is only 12K) will extract the needed information from a DAT file and format it as a GPX file.


DAT files can be downloaded for any county in the country from the NGS website.


Easiest way to use it is to unzip the download, then drop-n-drag a DAT file onto BMGPX.EXE. In a few seconds you'll have a GPX file to be imported into USAPhotoMaps. The GPX file will be quite large because each PID will have a lot of imported data fields.


Here's an ArtMan hint: once you have your benchmarks displayed in USAPhotoMaps, move one of the dots slightly — perhaps to slide a mark to coincide with the representation on the map. Once you make a change, USAPhotoMaps will rewrite the GPX file, but it will strip away all the unneeded fields an leave you with a lean, quick-loading file.


Example, using Charlottesville city, VA

The DAT file is 57K

The GPX file is 85K

The GPX file is 3K after unneeded fields are deleted, as described above.


What unneeded fields? Here's an original GPX entry for one PID in RED, followed by the stripped-down version in GREEN:

<wpt lat="38.028611" lon="-78.476944">








<Groundspeak:cache id="-2040449" available="True" archived="False" xmlns:Groundspeak="http://www.Groundspeak.com/cache/1/0">



<Groundspeak:owner id="0"></Groundspeak:owner>

<Groundspeak:type>Unknown Cache</Groundspeak:type>




<Groundspeak:country>United States</Groundspeak:country>


<Groundspeak:short_description html="True">NGS Datasheet</Groundspeak:short_description>

<Groundspeak:long_description html="True"> <h1>455.68</h1> <b> PID </b> HW0449 <br> <b> STATE/COUNTY</b> VA/C OF CHARLOTTESVILLE <br> <b> USGS QUAD </b> CHARLOTTESVILLE EAST (1997) <br> <p> <h2>Current Survey Control</h2> <hr> <b> NAD 83(1986)</b> 38 01 43. (N) 078 28 37. (W) SCALED <br> <b> NAVD 88 </b> 138.608 (meters) 454.75 (feet) ADJUSTED <br> <hr> <b> GEOID HEIGHT</b> -32.53 (meters) GEOID03 <br> <b> DYNAMIC HT </b> 138.512 (meters) 454.43 (feet) COMP <br> <b> MODELED GRAV</b> 979,937.8 (mgal) NAVD 88 <br> <p> <b> VERT ORDER </b> SECOND CLASS 0 <br> <p>The horizontal coordinates were scaled from a topographic map and have an estimated accuracy of +/- 6 seconds. <p>The orthometric height was determined by differential leveling and adjusted by the National Geodetic Survey in June 1991. <p>The geoid height was determined by GEOID03. <p>The dynamic height is computed by dividing the NAVD 88 geopotential number by the normal gravity value computed on the Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 degrees latitude (g = 980.6199 gals.). <p>The modeled gravity was interpolated from observed gravity values. <p> <table border=1><tr><td> </td><td> North </td><td> East </td><td> Units</td><td> Estimated Accuracy</td></tr><tr><td>SPC VA S </td><td> 1,188,140. </td><td> 3,502,020. </td><td> MT</td><td> (+/- 180 meters Scaled)</td></tr> </table> <p> <h2>Superseded Survey Control</h2>

<p> NGVD 29 (??/??/92) 138.851 (m) 455.55 (f) ADJ UNCH 2 0 <br>

<p>Superseded values are not recommended for survey control. NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums. See file dsdata.txt to determine how the superseded data were derived. <p> <h2>Marker Information</h2>U.S. NATIONAL GRID SPATIAL ADDRESS: 17SQC214119(NAD 83) <br>MARKER: Q = CHISELED SQUARE <br>SETTING: 30 = COPING <br>STABILITY: D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY <br> </table> <p> <h2>History</h2><table border=1><tr><td>Date </td><td>Condition </td><td>Report By</td></tr><tr><td>UNK </td><td>MONUMENTED </td><td>USGS</td></tr><tr><td>1935 </td><td>GOOD </td><td>NGS</td></tr> </table> <p> <h2>STATION DESCRIPTION </h2> <p>DESCRIBED BY NATIONAL GEODETIC SURVEY 1935 AT CHARLOTTESVILLE. AT CHARLOTTESVILLE, ALBEMARLE COUNTY, ABOUT 300 FEET SOUTHEAST OF THE CHESAPEAKE AND OHIO RAILWAY STATION, AT THE SOUTH END OF THE CROSSING OF THE LONG STATE HIGHWAY 239 BRIDGE, ON THE TOP OF THE EAST CONCRETE COPING OF THE APPROACH, AND 1.5 FEET FROM THE SOUTH END. A CHISELED SQUARE. </Groundspeak:long_description>

<Groundspeak:encoded_hints />

<Groundspeak:logs />

<Groundspeak:travelbugs />




<wpt lat="38.028611" lon="-78.476944">






Here's the text of the Readme file —


The purpose of this program is to convert the .dat files available from the

National Geodetic Survey to GPX files that can be read by the many free

programs that are available to geocachers. This program is a command-line

program, so you should be familiar with the command prompt.




Just put the file bmgpx.exe somewhere in your path.


*** TO USE:


Before using this program, you need a .dat file. To get a .dat file, use

your web browser to go to http://www.ngs.noaa.gov/cgi-bin/datasheet.prl ,

click on the "ARCHIVED DATASHEETS" button, then click on the "YEARLY_ARCHIVES"

button. Select your state and click "GET COUNTY ARCHIVES". Select the

county you want and in what format you want to receive the data, then click

the "Download File" button.


When you have the file, uncompress it if necessary. Now you're ready to use

bmgpx. If I've downloaded the .dat file for Allen County, Indiana, I would

type this:


bmgpx in003.dat allen_bm.gpx


in003.dat is the name of the .dat file I downloaded from the NGS website.

allen_bm.gpx could be any name, but I chose one that tells me what's in the

file. Now I can use allen_bm.gpx with EasyGPS, GPSBabel, Watcher, or any

other program that can work with gpx files.


For more detailed usage information, including hints on usage with Unix

pipes, type "bmgpx -h"


Starting with version 1.06, bmgpx will automatically generate an output

filename from the input filename if you provide only the input filename.

Previous versions would write the output to standard output. If you were

counting on the old behavior, you'll have to use shell redirection to

achieve the desired result:


bmgpx <in003.dat


This change allows bmgpx to be used as a drop target. Just drag a .dat

file and drop it on the bmgpx icon and it'll automatically generate a

.gpx file in the directory where the .dat file is.

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I was struck by the bucks that Delorme is charging for data available for free from NGS. Looks like $39.95 per state (or partial state for big ones). OK, you would have to download each county DAT file and convert it to GPX files (which I have one for the 4 -5 counties around me). But - wow!! Serious money for taxpayer owned data. I wonder if they get many takers.


By the way I use Delorme TopoQuads. Works quite well. I also use Geocaching Swiss Army Knife (GSAK) software to go from the GPX to a Delorme format .txt file that will import into TopoQuads. Summary:

NGS .dat file -> BMGPX -> .gpx file -> GSAK -> .txt file -> Delorme TopoQuads

Gives you whole counties at a time, onto genuine USGS 7.5 minute topo maps.

I also get files from GSAK for my Palm T3 PDA (Cachemate), and direct write file for my Magellan Meridian (SDD card writer, very fast). Ditto for caches from PQ's.


Anyone needs details, email me thru GC.com


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