Laser Technique Assessment in GIS data Acquisition

POEC 6383

by

Tianyou Chen

Rui Ge

November 5, 2001

Assessment Task description

The purpose of this technique assessment is to acquire laser mapping equipment for GIS spatial data acquisition in utility mapping (power poles, fences, gas line, gas valve, water pipe, water valves, etc), construction (construction layout), and digital geology data acquisition (geologic feature, terrain etc.). These tasks ask for both low accuracy (decimeter-level) and high-accuracy (sub-centimeter) equipment and that’s what we will be looking at in this report.

Necessity analysis

The reasons that we need these instruments are of the following:

  1. Laser mapping in addition to high accuracy GPS will speed up the procedure of acquiring high accuracy 3D spatial data. The continuous mode of the laser equipment will allow fast high-accurate local terrain building (such as a section for geologic analysis)
  2. Laser mapping extends the function of GPS in that it can map targets where GPS does not work well or work at all (under a big tree canopy, inside tunnels, etc)
  3. Laser mapping with its reflectorless function will reach targets that are far away (500 m) and are inaccessible by human.

In summary, it provides an efficient and cost effective way to acquire spatial data for GIS.

Technical Basics

The laser techniques can be used to acquire three dimensional data because its ability to measure the distance of the instrument reference point to a target using the Near Infrared or red laser (Light Amplification by Stimulated Emission of Radiation) beam plus the horizontal and vertical angle related to the target. The accuracy of the data depends on how accurately these parameters are measured. The way of measuring the angle is either using magnetic compass (1º) or encoder (0.1º to 1").

Technical Assessment Standards

For assessment standards, we will focus on the following aspects and skip other physical details:

  1. Accuracy, which includes, of course, distance and angle (horizontal and vertical)
  2. Functions, that is to see whether it supports that functions we need. Including:
  3. support reflectorless mode / non-prism mode
  4. motorized – can facilitate work but not crucial for us
  5. auto-tracking – for high-accuracy, one man operation
  6. Continuous mode, important for mapping geologic features and other continuous targets (river edge, road edge, etc)
  7. remote control (one man operation), not very crucial for our work
  8. Performance
  9. Range, how far a target it can map, especially in digital geologic mapping
  10. Measurement time: how fast can it measure, a very important factor especially when performing continuous measuring.
  11. Ease of use
  12. External interfaces: for data exchange between instrument and field PC or data logger. This is almost standard for all the instruments.
  13. Display. A bigger and better display makes it user friendly
  14. Does it support GPS integration (can be done later, not crucial)
  15. Laser plummet (makes it easier to set up the tripod)
  16. Cost

Technology Assessment Focus

We will compare two low caliber (accuracy) laser instruments from two leading companies -- Laser Atlanta (Advantage) and MDL (LaserAce and Quarryman ALS). Then we will compare two high caliber instruments (total station) from Topcon (GTS800 series/GPT-2000 series) and Leica (TCRA1100 series)

Company briefs

Laser Atlanta Optics¹, Inc., Norcross, GAUSA, has been manufacturing eye safe laser systems since 1989.

Measurement Devices Ltd² (MDL) is a leading designer and supplier of laser measurement systems. Company located in UK.

Topcon America Corporation³ is a world leading manufacture of surveying, GPS and other industrial instruments

Leica Geosystem 4 is a globally active surveying and geomatics technology group that provides systems for high-accurate 3D data capturing. It is based in Switzerland.

Advantage vs. LaserAce/ALS

The following Table compares the technical standards we have set up for the assessment. The green colored text shows a superior aspect to other products. From these comparisons we provide suggestions.

Analysis and suggestions

  1. Advantage is better than LaserAce in:
  2. Range (600m)
  3. Angle accuracy (0.01°)
  4. HUD display
  5. GPS integration
  6. LaserAce is within the same price range as Advantage and a little better in distance accuracy (10 cm to 15 cm) but inferior in:
  7. Range (300m)
  8. Angle accuracy (0.2°)
  9. MDL Quarryman is superior of all but:
  10. very specialized and expensive and less portable

Thus we suggest that

for general purpose laser mapping, choose Advantage because of the above superiorities over LaserAce with a reasonable price.

Topcon products vs. Leica products

The following table compares the Topcon GTS800 series /GPT2000 series and Leica TCRA1100 series. We then make our suggestions based on the analysis of the table. Again, green text means superior to other products.

Range *

Analysis and suggestions

  1. GTS800 series is superior in accuracy and in other aspects but:
  2. Do not support reflectorless
  3. Expensive
  4. GPT2000 series
  5. Supports reflectorless mode
  6. Quick measuring time and
  7. Reflectorless tracking mode
  8. Cheaper
  9. Leica TCRA1100 series
  • All in one
  • Very expensive

Thus we suggest that GPT2003 will be a good choice for doing high accuracy general purpose mapping because of its support for both prism and non-prism mode with a reasonable price.

Conclusion

We came up the following conclusions.

  1. For low accuracy, Advantage laser range finder from Laser Atlanta is a choice for its better performance (600m range) and higher accuracy(0.01°)
  2. For high accuracy, Topcon GTP2003 is selected for its support for reflectorless mode and tracking mode, and cheaper price

Reference

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