I do freelance video, and I've been hired by a delivery company to get some shots that will help in the investigation of an accident that happened a few months ago. They want me to set up the camera in a few locations, including inside the truck, to show what the driver could and/or could not have seen.
I was thinking that it would be pretty slick if I provided the client with GPS coordinates of every camera location that I use.
My quesiton: I know how to save my current location on the C530, and I know how to extract the GPS data from my saved places. But is the C530 accurate enough for the data I collect to be considered "legally" accurate?
In other words, if I'm holding the C530 in my hand, next to my camera & tripod, and if I "save" that location, are the GPS coordinates it saves equally accurate as the handheld GPS units that outdoorsmen & hikers use? Or are car-based units like the C530 a little less accurate when it comes to pinpointing and saving an *exact* location?
I am not a lawyer but . . . doubt you would be advised to specify accuracy yourself anyway, because that's just not something you can do without some serious challenges in court if someone chose to do so. You could only cite the manufacturer's specification data, which is printed in their literature and on their website, and can surely be backed up by Garmin. So, is +/- 3 meters accurate enough for the hassle? What does "exact" mean?
And I cannot speak to your question re relative accuracy of car units vs. handheld units. I know on our newly renovated golf course a company was hired to come in with backpack mounted units to map out sprinklers and other such permanent items to create various overlays for the course map, and they specified some pretty close tolerances of accuracy, much better than what my Garmin C530 will do, but I don't remember their figures. I guess different units are built with different end uses in mind, huh . . .
I have both a nuvi 350 and a eTrex legend handheld and don't see any difference in accuracy. I have used them both at the same time for geocache and they located the same point within about 3 feet. The accuracy depends on a lot of variables. The number and position of satelites acquired determines the accuracy at any particular time. Also when WAAS is enabled the accuracy depends on the location and number of WAAS satelites acquired.
There's probably not much difference between the accuracy of a handheld GPSr vs a car unit, but neither of these are going to be "exact". The best you are going to get is about plus or minus 5 meters.
If you want something that is more accurate, you'd probably have to look at one of surveyors grade unit. These can cost several thousand dollars.
there is really no way that the measurements could be considered legally sufficient. As accident investigation is an exact science involving distances, times, friction co-efficients, etc. the best you can do is give your employer a good idea of distances and locations...
IMHO, I'd not invest a lot of time in this as I would be able to blow you out of the water in about 3 questions
And that could mean either you are on this side of the sidewalk or on the opposite sidewalk (with a different field of view). Not recommended for legal use.
Totally agree with the comments here. The accuracy,although very good, would never be good enough for court. Turn a GPS on, stationary for 30 minutes, download the track and take a look. It bounce round second to second sometimes by dozens of feet or more. And add to that the altitude is never right and moves by 50+ feet while stationary. Any lawyer would drive a truck through that data.
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