[GIS] Do’s and Don’ts for GPS Localization

gpsland-survey

We have recently purchased some new GPS survey gear (ProMark 500) and we have set up a localization around the town using some of the known survey marks.

While I'm pretty confident that I have got it right so far, I was wondering if anyone had any good tips for setting up a GPS localization. Is there is anything to watch out for, or things I can do to reduce any error.

Also if anyone has any good articles on the subject it would be greatly appreciated, I'm struggling to find anything good on the net.

EDIT: While I appreciate the general GPS surveying tips, I was more interested about Localization in general. Does having localization marks close together negatively affect result. Can you have to many localization marks? Things like that.

Best Answer

I had the pleasure of working with the foremost surveyor in my community on a few occasions.

He is actually "the surveyor" that businesses & government bring in to fix/correct inaccurate surveys.

In my case, I am not versed in surveying techniques, but I do have the basics pretty well figured out. I have been out capturing x,y,z data for the purposes of watershed analysis, and I've also been out in the field capturing data from test pits and drill collars for the purposes of Hydrogeological studies.

First off, the Geodetic equipment "does" report your accuracy values, so if you're getting sub-centimetre feedback while in the field, you should be just fine. As far as your question regarding "good tips", the most important information that the surveyor mentioned to me was as follows:

  • Find a nice open area for your base station, BUT, also look for an area that will shelter your equipment from the possibility of theft.

What he did, is start at a known benchmark (an IB), then he moved his receiving station to an arbitrary location that provided good communication with the satelites, but was also "not" visible to passers-by. You would be surprised what people will steal (even if they don't know what it is, if it looks like it might be worth some money ....).

  • Watch your weather as part of you planning process. Heavy cloud cover can really throw a monkey wrench in to your day.

  • He also told me these units don't like evergreen trees. Try to stay away from an area heavily forested with conifers if you can.

If you're shooting in a dense forest that is mostly coniferous, you'll need the backpack unit and antenna. His unit however, is about 3-years-old.

That said, this may no longer be an issue with the newer units (just telling you what he shared with me).

  • This one is important!! He said when you're going to be conducting field survey for multiple days, always try to pinpoint something permanent as a location for your base station.

If you're signal starts getting weak, it might be time to plant a rod somewhere (ex - at the top of a bedrock outcrop) or to find another survey monument to move to.

He stressed the importance of this one!! He said, "even if I have to come back 2 years from now, I can be rest assured that I have plenty of survey benchmarks to utilize if need be".

What this accomplishes, is that you have a "known" that is easy-to-locate/return to, that is nicely situated (reception, protected from theft), and relatively permanent. This school of thought ALSO shaves huge amounts time off of the set up process the next day, next week, a year later .....

  • Lastly, have an axe (if you're in remote/forested areas), lots of batteries, etc, etc. In short, be prepared.

I am envious!! That's a nice toy. Hope these suggestions are helpful, and have fun!!

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