Some Common Issues that Ruin GPS Measurements and Projects

Some Common Issues that Ruin GPS Measurements and Projects

GPS receivers don't work under trees. GPS antenna needs to be above your head/body. GPS is difficult in urban canyons. If you want to work in difficult conditions, get PM500's with GLONASS.
More satellites = more easy = faster = better.

Holding receiver with antenna pointed towards the ground (or some direction other than up.) Consider using external antenna.

Holding the receiver directly next to a pipe or pole (or under a tree) when measuring position. Consider measuring with offset.

Not allowing enough time for position to fix or init while running static or Stop and Go shots.

Wrong Reference Frame. Mismatched epoch dates. Wrong datum (NAD83 vs. NAD27). (See above.)

Feet or Survey Feet. What is the difference? (1 foot = 0.3048 meters; 1 survey foot = 0.3048006096 meters)

Ellipsoid elevation or Orthometric elevation. NAVD88 or NGVD29?

Grid or ground distances?

Wrong equipment for the job. You can't measure sewer inverts to 1 cm and measure rim shots to 1 meter if you are running a flow study. You need a 1 cm rim shot too.

Ignoring productivity: If you are going to shoot 30 shots per day, a static PM3 pair or PM3.RTK or PM500 will all do a great job. But if you want to store 1,000's of points per day or
stake hundreds of shots per day, then dual-frequency RTK with GLONASS will make you much more productive.

Mission Planning: what's mission planning? There are times during every day when it is probable that you will have a low satellite count. Static shots will take twice as long, it will
take 4 minutes to fix a PM3.RTK pair instead of 10 seconds. If you don't want to mission plan, purchase PM500's with GLONASS so you always have plenty of birds in the sky. If you are willing to take a break for 30 minutes and wait for some more satellites
to rise, then consider PM3 receivers.

Figuring out what you are doing wrong after you have spent an entire summer systematically collecting poor quality data.
http://www.gps.gov/technical/ps/2008-SPS-performance-standard.pdf

http://140.121.160.124/gps/error.htm
http://www.spirent.cn/Solutions-Directory/~/media/Datasheets/Positioning/Application%20notes/DAN003%20Issue-1-01%20Fundamental%20GNSS%20Receiver%20Characterisation_CN.ashx

http://www.esalq.usp.br/departamentos/leb/disciplinas/Molin/ler5857/Arquivos/GNSS/ION_STD_101_RecommendedTestProcedureforGPSReceivers.pdf