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GPS on Benchmarks are still needed
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4/1/2014 at 8:21:23 PM GMT
Posts: 4
GPS on Benchmarks are still needed
The program goes on even though it is not National Surveyor's Week. The NGS still needs our participation in this effort to improve the geoid model in Georgia. If you committed to participate and were not able to do so, it is not too late.

Please visit the ngs web site for instructions 

4/1/2014 at 9:12:40 PM GMT
Posts: 4
GPS on Benchmarks description

To the Professional Surveyors of Georgia,

            There is a national effort being endorsed by the National Society of Professional Surveyors (NSPS) and the National Geodetic Survey (NGS) to improve benchmarks in the USA. Our state organization of SAMSOG and the Geospatial Committee hopes that each chapter (if not each surveyor) will participate in this worthy endeavor. Below is a copy of the description of the campaign from the NGS web site.

            The geoid accuracy in Georgia is poor compared to other states. This effort will improve this accuracy on and around the benchmarks you choose to occupy. The map below shows the areas in need of improved accuracy. Most of Georgia is included in the poorer areas. This campaign could help us a lot for future survey vertical accuracy.

            The best scenario would be to occupy several benchmarks in your area during and after National Surveyors Week. The more we can occupy, the better GPS derived heights will be in the future. A coordination effort should prevent duplicate observations.

            Please send this information to your chapter members and organize a local campaign to occupy as many benchmarks as you can during National Surveyors week. Public places would be good so the surveyor can be seen and be given a chance to explain a little about surveying to the public.

Here is the link to the NGS page

            Please send me a report of your chapters interest and their commitment to this campaign. Please Do Not wait until your next scheduled meeting! The planning and coordination will not take a lot of time and your members will need to make plans to participate.

            Once you receive an OPUS report on a benchmark, please forward it to me so I can keep a tally on the number our state completed. If I can be of assistance, please call me. My contact info is at the bottom of this email.

2014 GPS on Bench Marks Campaign

NGS encourages anyone with survey-grade Global Positioning System (GPS) receivers to join the 2014 GPS on Bench Marks Campaign, a National Surveyors Week (March 16-22) event to raise awareness about professional surveying while improving the National Spatial Reference System (NSRS).


Why Participate?

The nation’s height system, the North American Datum of 1988 (NAVD88), is founded on historic geodetic leveling surveys on thousands of bench marks that are often difficult and expensive to access. By adding GPS coordinates to these marks, the height system can be modeled in GPS survey systems for easier access. The latest hybrid geoid model,GEOID12A , includes many “GPS on bench mark” observations, but would benefit from additional data collection in many areas


How to Participate:

1.     Find local bench marks using the NGS Data Explorer or DSWorld . Review the corresponding datasheet to make sure it is a 1st- or 2nd-order NAVD 88 bench mark. 

2.     Pick the best bench marks to help improve the nation’s height system. If using DSWorld, view the GEOID12A accuracy map, and prioritize NAVD 88 bench marks in the areas that are yellow or orange on the map.

3.     Visit your bench mark of interest and make sure it has a durable, stable setting, with good satellite visibility. 

4.     Record a description and take photos of the bench mark to aid future recovery. (See optional observer field log and preview the upload form)

5.     Collect your data following careful field procedures. You should:

a.     Collect a 4+ hour GPS data file

b.     Verify antenna type, height, and plumb

c.     Use a fixed height tripod (recommended), and brace the legs with sandbags or chain

6.     Share your data by uploading to OPUS using option 'share my solution.'.


What happens next?

NGS will use your data to improve the next hybrid geoid model, increasing access to NAVD 88, and enabling conversions to the new vertical datum in 2022.

Here is a map of the geoid uncertainties in Georgia. Green is +/- 2 cm, Yellow is +/- 4 cm, Orange is +/- 8 cm at the 95% confidence level. The goal is to turn this map completely green.

 Attached Images:

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