It depends on the accuracy you want. Generally speaking GPS is the fastest and easiest way. If you need more accuracy an RTK GPS can be useful, though some post processing is needed to obtain better accuracy.
You use DGPS for accuracy and if you don't have DGPS also use Toposheet to find out the location
For the accuracy at 1m or less a total,.static GPS station; for 5 m, a hand-held GPS will do assuming you know about projection systems of the topomaps and there transformation at you location. At the 10m a topographic map (1 : 25 000) would do.
As stated previously, it depends on the scale of the map. For example, with a map at scale 1:50000 we can use handheld GPS to determine your scale at +/- 3m.
Lately, I've been using a hand-held GPS, but in mountainous forests, sometimes I can't get a good signal. Then I have to go back to older methods, including recognizing where I am by finding a nearby object that I can identify on the ground and on the map, and measuring the direction and distance to my datapoint, or by resecting from 2 or 3 visible landmarks that I can locate on the base map, or using the map in combination with an altimeter to estimate my elevation along a stream, ridge or hillside. USGS has new 2:24K orthophoto quads with topography, and with both lat-long and UTM coordinates. This makes plotting coordinates or finding recognizable features on the map a lot easier than it used to be.
Art Bookstrom
One option would be, if you have one, use an RTK type unit and antenna to collect, say 5 hours of data over a monument at a place near where you want to isolate on a map (unless you want the monument to be the site, and you have clear access to at least 4 satellites (and keep an eye out for low PDOP during your sample time, as satellites may "stack on top" of each other, basically reducing the number of satellites. It seems to get worse the farther north you go, but you can get print outs of the times when low PDOP may be a problem and just work around it), drive your metal stake as deep as you can in case you need to reoccupy your monument (no wiggling), set the unit to Collect Data, and check the file occasionally to see if it is getting bigger. You can set the time of collection from say, 5 to 30 seconds per point recorded, then shutdown the unit, convert it to an OPUS (not an endorsement) file (should be choice in your software, and I'm trying to remember using Trimble (not an endorsement) as a reference, so your mileage may vary, and submit that data to NGS, and they will process that for you (I don't seem to remember have any issues with this part). Once you get the data back, if you shot RTK all the way down to your site, if memory serves, the software will self correct the data points. You can always use a total station or even a level to shoot down to the point of interest. It depends on how much work you want to do, and what kind of equipment you have access to for the level of accuracy you need, the total station being a bit easier, as your data should be able to be corrected/adjusted in OPUS. You're on your own if you use a level If you need specific information, let me know and I can put you in touch with someone that really knows this stuff. I'm working off of memory of work done 12 or so years ago, so I'm sure things have likely gotten easier, and my memory isn't what it used to be, so don't forget to bring a grain of salt. Best of luck...Bob
Normally we use Trimble, GARMIN and magellan GPSs to collect spatial locations. In the field you can take a printed gridded landuse map with latitude and longitudes marked in top bottom left and right sides of the map. There also u may include the road network for your easy reference. You can check the landuse map with the GPS location collected at the site and verified the location. But it depends on the accuracy of the GPS and the scale of the map u use.
Differential GPS (DGPS) is high-accuracy GPS, specially supplemented by ground-based stations, not just satellites. Those units are pretty expensive. As said above, it kinda depends on how much accuracy you really need. Smartphones are decent enough if you don't mind being a few meters off. When using a better commercial GPS receiver, try to get more than 4 satellite signals (3 is the trigonometrical minimum, 4 is the minimum the units work with, and more than that means greater accuracy).
When relating what the GPS receiver tells you to a map, remember that GPS lat/long readings are in the WGS84 datum; you might need to run those coordinates through a mathematical transformation if your map doesn't give you lat/long in WGS84 (e.g., American maps might give you NAD83, commonly). That detail might be trivial or major, depending on where on Earth you are. Some commercial units let you choose what coordinate system (i.e., datum) they output their readings in; just be aware of which system the receiver is reporting in.
Depending on the accuracy of the field work using map location. For topographic maps where the magnetic declination is stated, the true bearing from any physical feature identified on the map can be obtained, thereby giving an initial orientation with prismatic compass. This will be apt where the location inhibits signal reception for GPS.
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