GPS unit

B

Bus Driver

501 Club
Have never used a portable GPS unit. I would like one that could be used to identify the coordinates of obscure grave sites accessible only by hiking for example or property boundary markers plus be usable for driving as most of my vehicles are several years old.
Any unit suitable for both purposes? Recommendations?
A land surveyor told me that the unit available for their use costs $27,000.00. I was hoping to come in at a lower price!
 
Bus Driver, I have an older Garmin that will do what you want, although I've never used it for that. I'd suggest visiting an electronics or big box store and finding out which current models will do that so you can compare features and prices. I've had a surveyor out recently and their unit will locate within an inch +/_. The kind we can afford may only be accurate to within 5-10" (approximately).

Bob
 
Take along a friend with a smart phone. :D

37.729711, -91.457292

Copy and paste the above line into Google and select Maps and then change to Earth view and zoom in. Say hi to my great great great grandfather. I took a reading off my smart phone while there. Used it to show some of the other relatives where it was.

OK, I couldn't find the old email to get the exact coordinates from a few years ago so I went to Google and copied them from there. My reading on my phone was off about 10 feet, from this one, but same end result. Any of the family could type it in and go right there without going "right there".
 
I have a Garmin Nuvi 50LM that I have been pretty happy with for highway use. I don't believe it is a current model. Current models probably have functions similar to this one. When the map is displayed, you can touch the image of your vehicle and it changes to a display that includes latitude/longitude in the form of xx degrees xx.xxx minutes. I've walked the corners of my property with it and it seems to be pretty close, at the least very repeatable. Doing a "touch and hold" on the signal strength indicator gives a screen that includes position and signal strength and computed accuracy. Right now, sitting on my desk it has been floating around something less than 100 feet. Outside, it is more typically 30 to 60. It seems to be able to run quite a while off the battery (never really tried it for long). It recharges from a lighter plug or a USB connection. Whatever you get, if you are going to use it in a car, get one with lifetime map updates.

Take a look at this page to see what Garmin has to say about accuracy. I can't find which if any of their units are WAAS enabled.
http://www8.garmin.com/aboutGPS/waas.html
 
I believe most of the current hand-held GPS units will do what you want to mark "waypoints" for locations of interest. I would stick with well-known makers such as Garmin and Magellan. Most of them can repeat within 10-50 feet, as long as you have a clear view of the sky.

For land boundaries, I do not know how useful it would be. You certainly do not want to build a fence along the line of a troublesome neighbor, for example, based on a hand-held unit. Even the $20k+ units will not help you that much. Not only are they complicated to use, but there is ALOT more to boundary surveys that simple measurements.

Trent J. McPeak, Illinois Professional Land Surveyor #035-003866
 
My intent is not to substitute for surveying. Most of my property is rural and wooded. Tall vegetation is reported to interfere with GPS function. My plan is to record the GPS coordinates of the boundary markers, some of which are planted stones from more than 100 years ago. I had hoped to be able to reliably get the coordinates within 3 feet of actual location. That may not be possible. 50 feet is perhaps helpful, but not very much for this purpose.
50 feet is more than adequate for driving directions.
My family shows little interest at this time in walking to each of these locations and probably will late regret that they do not know the locations. And occasionally, I will have some difficulty locating a marker after not seeing it for a few years.
One tract has had continuing problems with a succession of adjoining property owners destroying the boundary markers.
 
Acreage was surveyed before we purchased it. We used surveyor's map and son's older Garmin to locate and record the surveyor's stakes/markers. Then installed a fence on the property line where no fence existed.

The surveyor's stakes/markers were a combination of metal rods with yellow caps, wooden stakes, and a pile of rocks. The Garmin got us within about 3 feet of the markers.

Locating the surveyor's stakes/markers was a worth while exercise. We found out that the existing north/south fence on the west side of the property was located about 3 feet on our side of the property line. The east/west fence on the south side of the property was also not set on the property line. The east end of the fence was set about 4 feet outside our property and the west end was set about 10 to 15 feet inside our property.
 
I have a 4 year old Garman model that I used to collect location information for water meter positions, it will give location positions in degree/minutes/seconds or degree plus 5 decimal points. When the the information is used by the meter reading equipment, it will repeat within about 4 feet. I also use it for highway driving and have been very satisfied with it.
 
I have a Garmin eTrex10 handheld which is about the cheapest way to go if you mostly want to log positions. The display is mono, no color, but the accuracy is the same as the higher priced eTrex models that have more features. It will store 500 waypoints and 2 AA batteries will last tens of hours. You can also average a waypoint for as long as you want to increase position accuracy. I did this on my property corners for about an hour at each corner and placed them on google earth and they were all about 2-3 ft off, all in the same direction. So that means the receiver has good precision, but the accuracy is fair (for a handheld).
The accuracy spec with WAAS enabled corrections is <3 meters 95% of the time, which also means <1.5 meters 67% of the time.
A good buy for the money, about $130, to increase the accuracy the price goes up real fast into the thousands.
 
If you're going to pick up a new or used receiver, I think the most important feature to look for in an inexpensive handheld is WAAS enabled corrections. For the last many years, corrections are calculated and up-linked to WAAS satellites and rebroadcast via satellites to receivers which improves accuracy. These WAAS satellites transmit on the same frequency as the GPS satellites and can also be used for ranging calculations as well as for corrections. Before that, and still in operation are beacon transmitters located around the USA. These base stations have a precisely surveyed in position, and by receiving GPS, calculate a position. There is then an error due to constellation, atmospheric delays, etc which is encoded into "corrections" and transmitted by a low frequency station and requires another, special receiver to be connected to the GPS receiver, either internally or externally. These corrections are then decoded and applied by the GPS receiver resulting in sub meter performance, but not survey quality. WAAS operates in a similar manner, but covers a larger area and does not require a special receiver, just special software to decode and apply the corrections.
For the recreational user, WAAS is the only economical way to get corrected GPS positions.
 
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