Notes and Suggestions for Botanical Garden Surveyors - Part 12
ByWalt Dunlap, Mapping Specialist, The New York Botanical Garden
As a mapping specialist at The New York Botanical Garden and a professional land surveyor for the last 20 years, I am offering consulting services on land surveying to any garden that is mapping or planning to map their collections or garden.
For those BG-Map users who employ a data collector such as the HP-200LX palmtop, there is a powerful tool in the main program which allows storing coordinate values of the control points you use. Most garden mappers have a finite series of points from which they map their collections and structures. Often this list is maintained as a separate printout that is carried into the field for manual entry of coordinates.
There is ample opportunity for errors in this method. There is no inversing routine to check distance between back- and fore-sights as occupied to help ensure that the proper coordinates have been entered. True, you may double check the listed azimuth on the palmtop before uploading as a check but there is nothing automatically built in to give you a pause before beginning your locations. If the coordinate values are mis-entered for whatever reason (poor screen visibility, slip of the finger, smudged numbers, etc.) it may not be caught until the objects are imported into the base map and a row of trees appear in the middle of a path. Worse, the error may be small enough that it is not evident from the map relationships. Could you spot a 2’ or even 3’ error in the open? Recovering data from these problems is technically feasible but time consuming and usually not worth the effort. Most of us would go out and re-locate all the objects, keeping very quiet about the whole episode, right? Unfortunately that doesn’t prevent it from happening again and although we may have learned a lesson, it doesn’t necessarily apply to the next instrument operator.
The stations.fil file resides on your hard drive and your palmtop and it is easily transferred one to the other using the laplink or transfile 200 utilities. It is a simple ascii-type text file in this form:
being: point number, easting, northing, elevation
The elevation value is marked in this manner only as a place-holder if you are not using actual elevations. Be aware that if you do use an elevation the program will automatically assign elevations to all your located objects so you must be mindful of the procedures for that. (See the BG-Map manual)
By maintaining this list in the office with the notepad function and transferring it to the palmtop, you always have a list of control points ready and they will be accurate without doing any data entry in the field. Do the data entry in the office! Eschew errors!
During the setup routine and the request for station coords, whether for setup point or azimuth point, merely press the special function Ý key (up arrow) and the # key (gold color) and the point number <ENTER>. The setup coordinates are shown in the upper right corner of the screen. The azimuth will be displayed as usual when you enter the backsight point. Go from there.
Editor's Note: See Using Stored Station Coordinatesstor_sta.html for more information on this topic.
TO BE CONTINUED -
Updated February 6, 2002.
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