basic gps surveying techniques presented by: neil gray, teacher-in-charge, columboola eec. on behalf...
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![Page 1: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/1.jpg)
Basic GPS Surveying Techniques
Presented by:
Neil Gray, Teacher-in-Charge, Columboola EEC.
On behalf of ICT Innovators Centre, STiS Project.
![Page 2: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/2.jpg)
Surveying Techniques
3 Levels of GPS Surveying
• Point Positioning – uses stand alone receivers, taking measurements from the code carried on the signal. Many sources of error adding up to 10 – 15 metres with Selective Availability turned off.
• DGPS (Differential) – uses two receivers recording position data concurrently. One Base receiver is set up at a known position and the data from this is compared to rover data to allow a correction.
• Precision Surveying (Phase Observable) – differential technique based on the carrier phase, not the codes. Direct radio signal measurement results in errors being reduced to the mm-cm level.
![Page 3: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/3.jpg)
Point Positioning
• Uses recreational level GPS units. Any particular point measurement will be within 10-15 m of a known point. (Under ideal conditions, this error range could be worse under less than favourable conditions.) This reading will cycle around the point over time.
• Accuracy can be improved by averaging, that is by taking a minimum of 10 readings for a required point over a 10-20 minute period and averaging the results to determine the point.
•The results of this process are displayed on the following slides.
![Page 4: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/4.jpg)
![Page 5: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/5.jpg)
Surveying exercise completed for a single point. Data displayed using MapSource.
![Page 6: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/6.jpg)
UTM positions can be seen in the data table for the program. Note how similar most appear in terms of at least one parameter.
![Page 7: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/7.jpg)
The same points displayed in DNRGarmin. Note how different the points are now in terms of the cartesian coordinates (x & y proj.). This is because the program records the position without rounding off.
![Page 8: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/8.jpg)
The previous 10 records of the one position have been sent to a GIS for display. Here it can be easily seen how a GPS unit scatters the readings even though the readout might show an unchanging Cartesian coordinate!
![Page 9: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/9.jpg)
DNRGarmin can calculate a mean value, standard deviation and circular error of probabilities to enable statistical analysis and determination of the point (mean).
Click “Edit”
![Page 10: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/10.jpg)
The mean value can be used to create a new point in DNRGarmin. This can be saved to the GIS for display. Note the mean point positioned at the cross.
![Page 11: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/11.jpg)
The mean (known) value is actually none of the measured points but a best fit for the analysed records. The scattering of the records is caused by inherent errors in the GPS system used namely:
• Clock Errors
• Signal Multipath
• Dilution of Precision (SV constellation)
• Atmospheric Factors
• Human Error
All GPS based measurements need some degree of processing to improve base level accuracy, professional grade units have this feature built in at a significant cost.
![Page 12: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/12.jpg)
Other Surveying Techniques• Recreational GPS is affected by buildings, vegetation and fences.
• Surveying to these objects may require more traditional measurement techniques.
• Some options include – offset points or lines, measuring distances and bearings from known points.
![Page 13: Basic GPS Surveying Techniques Presented by: Neil Gray, Teacher-in-Charge, Columboola EEC. On behalf of ICT Innovators Centre, STiS Project](https://reader030.vdocuments.site/reader030/viewer/2022032801/56649d555503460f94a323da/html5/thumbnails/13.jpg)
Other Surveying Techniques
DGPS
• Base units with the software and a subscription to a DGPS service are costly ($1000’s).
Precision Surveying
• As above except the cost can now be very high ($10000’s).