| UNAVCO
 


GPS Data Collection Methods

GPS Data Collection Methods

Various methods are used to collect high precision differential GPS data. The particular method used depends on several factors, including survey objectives, desired precision, available equipment, and field logistics. Higher precision typically requires a more rigorous field methodology and longer occupation times. The following table shows the features of the most common GPS survey methods:

 

Survey style

Typical accuracy

Occupation time

Typical applications

Continuous

< 0.5 cm

Months or more

Crustal deformation, geophysics, reference stations

Static

0.5 cm – 2.5 cm

Hours to days

Crustal deformation, geodetic control, very long baseline surveys, geophysics

Rapid Static

1 cm – 3 cm

Minutes

Short baseline surveys, glaciology

Kinematic (post-processing and real-time)

1 cm – 5 cm

Seconds

Short baselines, closely spaced points, vehicle positioning, feature surveys, GIS and mapping

(not supported)

Code Differential

50 cm – 300 cm

Seconds

Coarse GIS, mapping, positioning

(not supported)

Point positioning

100 cm – 500 cm

Minutes to hours

Rough positioning

Continuous stations are continuously-operating long-term or permanent GNSS station installations involving immobile monumentation and sustainable power, and often involving data telemetry. The can be used as pre-existing base stations in campaign surveys (static, rapid static, and kinematic).

Static surveys are regional, sub-cm precision GNSS surveys with portable equipment and are the standard campaign data collection method for crustal deformation surveys. They typically involve occupying each point for several days to get the highest possible accuracy. Collect at least 6 hours of simultaneous data per day for processing and repeat benchmark occupations if possible.

Rapid static surveys are static surveys with just enough survey time at each point to be able to resolve the carrier phase integer ambiguity. A rule of thumb is to collect data for a minimum of 10 minutes per point, and add one minute of occupation time per kilometer of baseline length over 10 kilometers. For example, on an eight-kilometer baseline collect at least 10 minutes of data, and on a 28-kilometer baseline collect at least 28 minutes of data.

Kinematic surveys are local surveys (<10 km) using mobile GNSS equipment for the purpose of mapping features or of measuring point locations where several cm of precision is sufficient. At least two receiver set-ups are required: a base (stationary) unit and one or more rover (mobile) units. Kinematic surveys rely on continuous tracking to resolve the integer ambiguity; while the rover receiver/antenna may be moving during the surveys, continuous lock on the satellite signals must be maintained. Since the data processing software is able to both resolve the ambiguity and track the antenna motion, fixed-integer solutions are obtained nearly instantaneously.

Post-processing kinematic (PPK) refers to surveys without communication between the base and rover receivers. Processing the data after data collection is required. There are no navigational capabilities in PPK surveys.

Real-time kinematic (RTK) refers to surveys in which the base and rover receivers communicate corrections in real-time via a radio link. This requires additional hardware (base and rover radios) and additional power, and generally limits the survey to an area of several km, but eliminates the need for data processing and enables navigational capabilities.

Code differential surveys rely only on the code data to determine a differential solution. Simultaneous data collection between the base and rover receiver is still required, but there is no requirement to maintain continuous lock on the carrier phase since the phase data is not used. As a result, this method is extremely robust, but relatively coarse. For sub-meter accuracy, a rule of thumb is to collect data for five minutes per point, and add one minute of occupation time per five kilometers of baseline length over 10 kilometers. For example, on an eight-kilometer baseline collect at least five minutes of data, and on a 108-kilometer baseline collect at least 25 minutes of data.

Point positioning uses only data from a single receiver to determine its coordinates. The collected data are averaged, and longer occupations significantly increase the accuracy. This method is very coarse, but sometimes it is the only way to determine base station coordinates while in the field. Although these coordinates may be off by about a meter, it is close enough to allow the computation of precise baselines while at a remote field location. When better network accuracy is desired, the base coordinates must be re-computed when back from the field.

Attached Files
There are no attachments for this article.
Comments (3)
Comment by ravi chavda on Wed, Oct 5th, 2011 at 1:53 AM
no
Comment by SAEED KHAWAR on Sat, Aug 27th, 2011 at 6:33 AM
SO FAR THE BEST MANUEL I GONE THRUOGH IS RICS GUIDELINES FOR THE USE OF GNSS IN LAND SURVEYING AND MAPPING.YOURS ONE IS ALSO GOOD AS QUICK GUIDANCE.I AM LOOKING FOR A FIELD WHERE YOUR INSTITUTION HAVE ANY PROJECT IN PAKISTAN BUT DID NOT FIND ANY ,WE HAVE MANY GOOD THINGS TO DO EXCEPT EDUCATION GOD HELPS US .I AM IN SAUDI ARABIA AND WORKING AS LAND SURVEYOR ANYWAY I LEARNED A LOT IN YOUR SITE
Comment by arjun on Thu, Jun 9th, 2011 at 7:56 AM
i want some tools for tracking project
Name
Email
Security Code Security Code
Related Articles RSS Feed
UNAVCO Investigator Manual - Campaign Procedures
Viewed 1960 times since Tue, Nov 24, 2009
UNAVCO Trimble 5700/R7 Campaign Kit
Viewed 28992 times since Mon, Mar 22, 2010
UNAVCO Topcon GB-1000 Campaign Kit
Viewed 45281 times since Wed, Jul 14, 2010
UNAVCO Trimble NetRS Campaign Kit
Viewed 7386 times since Fri, Jul 30, 2010
English version of ICD-GLONASS version 5.1
Viewed 2723 times since Thu, Sep 29, 2011
UNAVCO Trimble NetR9/R8 Campaign Kit
Viewed 2138 times since Tue, Aug 23, 2016
Campaign Surveys - How to obtain high-confidence coordinates for a base station
Viewed 13996 times since Tue, Jan 26, 2010
Campaign Data Collection Modes and Memory Requirements
Viewed 3739 times since Wed, Mar 24, 2010
MENU

Last modified: Monday, 12-May-2014 00:18:29 UTC