Here’s a roadmap of use for better results:
1.- Choose a day with clear sky! (low i95). There are many sites in the internet providing real time i95 index data.
2.- Choose to measure, during early morning or late evening (usually i95 is lower).
3.- Start your device’s GNSS receiver 15 minutes before start, measuring. (You can do that by starting the app and entering measuring screen).
4.- If you know the exact coordinates of a point near your area of measurements, Perform a known point calibration, otherwise go directly to step 8.
5.- Put your phone exactly at the point of known coordinates. From the main app screen choose “Know point” calibration. The calibration procedure will start.
6.- Let the calibration procedure terminate (about 5 minutes) and then you will be prompted with the measured coordinates of the point. Modify these values by keying-in the true coordinates of the point and press Accept (the check mark. The calibration is completed and your point will be displayed on Google maps.
7.- Leave the map screen by pressing back (or the small left arrow on the upper left corner of your screen, in the left of the total station photo) and enter “Start Measuring”
8.- Put your phone at the point you want to measure on a wooden pole, or a pile of books or newspapers. (Surveying tripods have usually a metal plate on top. With most devices this is disastrous. So If you use a metal tripod put a pile of books between the metal plate or the device. A good alternative is to use a plastic tripod of a camera.)
9.- When you’re ready press “Start increasing accuracy” and wait for about 5-10 minutes (Measurements about H=300 – 600). Please always check hdop values before pressing “Start increasing accuracy”. Values must be around 1.0 – 1.3. If they are bigger, you’ld better wait some minutes till you see better values. (The app uses every measurement with a hdop value between 1.0 – 3.0 (Depending on the settings). Use DOP < 1.3 for accurate measurement. Use DOP< 3.0 for faster but less accurate results.
10.- Press “Stop increasing accuracy” and then add the point to the list of points.
11.- Repeat steps 8-10 for every point you want to measure.
12.- After having finished with all points, save your list of points and leave the field.
13.- If you haven’t perform the “Know point” calibration you can apply off line corrections to your measurements. (you can find the appropriate correction values in the internet. Most RTK & SBAS correction services provide off line correction tables.
Do all of your measurements at the same time! Measuring one point in the morning and one in the night will lead you to increased inaccuracy! If you can avoid doing measurements at different times there is a trick you can use. Before each measurement do a “Known Point” calibration at the exact same point. Even if you don’t actually know the exact coordinates of the point, you can do the following trick:
a) Do a “Known point” calibration at a point. Accept the coordinates you’re prompted with, and write them down. b) Later on the day, or the next day, or whenever, return to the point and perform again a “Known point” calibration at the exact same point. At the prompt insert the coordinates that you’ve written down the day before. c) Repeat this every day you return to the same field. This trick ensures that even if the measurements are not exactly accurate will have the same error vector!
I hope these will help…