--- title: "GPS field procedure" subject: "Surveying II" chapter: 8 key: "semester_4/surveying_ii:gps-field-procedure" source: https://www.bctengineer.com/q/semester_4/surveying_ii/gps-field-procedure site: BCT Engineering --- # GPS field procedure Surveying II · Chapter 8: Field Astronomy and GPS - Asked in: 2070 Magh, 5 marks - Video: [Best Practices for Static GPS Surveying | Step-by-Step Guide for Accurate Geodetic & Control Surveys](https://www.youtube.com/watch?v=-329pENX34E) — Geospatial Solution - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/surveying_ii/gps-field-procedure - Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-8 ## Question Explain in brief GPS field procedure. ## Short answer GPS field procedure involves planning sessions with good DOP, selecting stations with clear sky above 15° and no multipath sources, and setting up the antenna centered and leveled. Observe by logging data with set interval and antenna height, then download, process baselines, adjust the network, and check closures against known points. ## Answer The field procedure of a GPS survey (static or kinematic relative positioning) is: 1. **Reconnaissance and planning:** study the project area, the existing control points and the sky visibility. Plan the network, receivers, observation sessions and baselines. Check the satellite availability and DOP (mission planning), and choose a time with good geometry (PDOP below about 6). 2. **Selecting stations:** points should have a clear view of the sky above about 15° elevation, and be away from reflecting surfaces (multipath), power lines and transmitters. 3. **Setting up the receiver:** the tripod and antenna are centred over the station mark with an optical plummet and levelled; the antenna height is measured (before and after observation) in two or three places, and the antenna is oriented to north if required. 4. **Observation:** switch on the receiver, set the recording interval (e.g. 15 s) and elevation mask, enter the point name and antenna height, and log data for the session length (static: 30 min to several hours depending on baseline length; RTK: a few seconds per point). 5. **Record keeping:** field sheets record the station name, receiver and antenna numbers, date, start and end times, antenna height and weather. 6. **Data download and processing:** the data are downloaded to a computer, baselines are processed, and loop closures and quality checks are done. The network is adjusted and the coordinates are transformed to the local datum. 7. **Checking:** some baselines are repeated as a check, and results are compared with known points. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is checked in the planning stage of a GPS survey? A. Satellite availability and DOP, choosing a time with good geometry (PDOP below about 6) B. Only the weather forecast and receiver battery C. The temperature and pressure for EDM correction D. Only the antenna height Answer: A. Mission planning checks satellite availability and DOP so that observation is done when geometry is good. (Key point: Mission planning) 2. Which condition makes a good GPS station? A. Close to tall buildings so signals bounce and reach the antenna B. Clear sky view above about 15° elevation, away from reflecting surfaces and power lines C. Under tree cover to protect the antenna D. Beside a transmitter tower for a strong signal Answer: B. A clear sky view avoids blocked satellites, and keeping away from reflectors and electrical interference reduces multipath and noise. (Key point: Station selection) 3. How is the antenna set up over the station? A. Placed beside the mark and the offset is estimated B. Levelled only, with height measured once after observation C. Centred with an optical plummet, levelled, and the height measured in two or three places before and after observation D. Centred by eye and height read from the receiver display Answer: C. The tripod is centred over the mark with a plummet, levelled and the antenna height measured several times. (Key point: Antenna set-up) 4. What determines the observation time of a session? A. Every method needs exactly 30 minutes B. Static takes seconds and RTK takes hours C. It depends only on the number of tripods D. Static needs 30 min to hours depending on baseline length, while RTK needs only a few seconds Answer: D. Static sessions are long and depend on baseline length; RTK needs only a few seconds. (Key point: Observation session) ## Related in Surveying II - [GPS field procedure and components](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agps-field-procedure-components) — Surveying II, chapter 8 - [Traverse field procedure between two known stations](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atraverse-field-procedure-between-known-stations) — Surveying II, chapter 1 - [Field procedure of aerial photogrammetry, relief displacement](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aaerial-photogrammetry-field-procedure-relief-displacement) — Surveying II, chapter 7, asked 2× - [Three-wire stadia field procedure for topo map](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Athree-wire-stadia-field-procedure) — Surveying II, chapter 2 - [Stadia principle and field procedure](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Astadia-principle-field-procedure-topo) — Surveying II, chapter 2 - [ODM principle, tacheometric field procedure](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aodm-principle-field-procedure-theodolite) — Surveying II, chapter 2 ## Related in other subjects - [Field procedure of chain surveying](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Afield-procedure-chain-survey) — Surveying I, chapter 3, asked 4× - [Field procedure of compass traversing](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Acompass-traverse-field-procedure) — Surveying I, chapter 4