COMPARING AND CONTRASTING THE VARIOUS SURVEY METHODS FOR PROPERTY DEFINITION. by David Jonas, Spatial Solutions Consultant

Transcription

1 COMPARING AND CONTRASTING THE VARIOUS SURVEY METHODS FOR PROPERTY DEFINITION by David Jonas, Spatial Solutions Consultant

2 PRESENTATION OUTLINE 1. Department of Land Resources have outlined acceptable Survey Methodology and Deliverables for Digital India Land Records Modernisation Programme (DILRMP) 2. These are meant for guidance to the States / UTs and they are at liberty to accept / modify any / all of these guidelines 3. This presentation will compare and contrast the survey methods listed 4. Close with review of processes to maintain and monitor future changes to property boundaries.

3 Acceptable Survey Methodologies

4 ACCEPTABLE SURVEY METHODS Field Survey: Electronic Total Station Differential GPS Remote Sensing: High resolution satellite imagery Aerial Photography Other Methods which can be Explored Unmanned Aerial Vehicle Terrestrial LiDAR Mobile LiDAR Aerial LiDAR.

5 GPS / ETS FIELD SURVEY Features: Property survey sits on a Hierarchy of Survey Marks Property boundaries recorded by brief GPS occupation, or ETS radiation Pros: Highest pointing accuracy Visiting property boundaries often accompanied by land owners Cons: Visiting property boundaries often accompanied by land owners Requires access to, or visibility of, every property corner Very slow: survey undertaken at walking pace after negotiating site access Difficult to define non-linear boundaries No auditability, as field party visits only once.

6 SATELLITE IMAGERY 30 cm Satellite Imagery of Delhi

7 SATELLITE IMAGERY 30 cm Satellite Imagery of Delhi

8 SATELLITE IMAGERY Features: Range of platforms including Cartosat, Digital Globe, Pros: No mobilisation costs Can provide the 3 rd dimension with stereo coverage Cons: Accuracy doesn t really meet stipulated 1:1000 specifications Low resolution makes more difficult to recognise subtle land boundaries.

9 TRADITIONAL AERIAL PHOTOGRAPHY TRADITIONAL AERIAL PHOTOGRAPHY

10 TRADITIONAL AERIAL PHOTOGRAPHY TRADITIONAL AERIAL PHOTOGRAPHY

11 TRADITIONAL AERIAL PHOTOGRAPHY Features: Large frame cameras, fitted with GPS and IMU Pros: Provides property framework efficiently and accurately Well understood in the Indian market Large resource in India to process orthos Resultant orthophotos provide valuable data layer for other Govt uses Cons: Requires field completion of boundaries obscured by vegetation Requires DGCA/DRI security permits (takes 2 to 3+ months) Mobilisation costs make it less efficient for small areas Require more flying (cost, time and weather risk) than modern cameras.

12 MODERN AERIAL PHOTOGRAPHY New Technology: eg. VisionMap A3 Allows wider capture per run

13 MODERN AERIAL PHOTOGRAPHY VisionMap A3: Rotating Head Camera

14 MODERN AERIAL PHOTOGRAPHY MODERN AERIAL PHOTOGRAPHY

15 MODERN AERIAL PHOTOGRAPHY Features: Rapid capture from frame camera with long focal length Every ground feature appears on many frames Allows image capture 2-3x higher than traditional cameras Suits very large areas (10,000km 2 +) Pros: Same as for Traditional Aerial Photography Less flying means lower aviation costs, less time, and less weather risk Redundant imagery allows automatic processing (quicker, cheaper, robust) Cons: Same as for Traditional Aerial Photography Specialised processing means less capability in India.

16 ACCEPTABLE SURVEY METHODS Field Survey: Electronic Total Station Differential GPS Aerial Remote Sensing: High resolution satellite imagery Aerial Photography Other Methods which can be Explored Unmanned Aerial Vehicle Terrestrial LiDAR Mobile LiDAR Aerial LiDAR. 1. Accuracy 2. Accessibility 3. Resolution 4. Land holder familiarity 5. Auditability 6. Permissions 7. Timeframes 8. Other Applications.

17 COMPARING FIELD VS AERIAL Field Survey Accuracy: centimetre / decimetre Accessibility: Need access to, or visibility of, every property vertex Inaccessible vertices incomplete Resolution: Non-straight boundaries difficult Land holder familiarity only linemap to describe boundary Aerial Remote Sensing decimetre (AP) / metre (satellite) Need to see every property vertex from above Vertices under trees incomplete Non-straight boundaries easy Rich imagery to describe boundary

18 COMPARING FIELD VS AERIAL Field Survey Auditability: No accountability of correct pointing Permissions: Property owner permission to enter Timeframes: Quick start-up, slow acquisition Resources Limited by equipment availability Other Applications: Able to leave monumentation Aerial Remote Sensing Pictorial archive provides audit and legal traceability DGCI/DRI permission for survey Slow start-up, quick acquisition Vast photogrammetric capacity Othos and DTM vital data layers.

19 Other Mentioned Survey Methodologys

20 UAV PHOTOGRAPHY

21 UAV PHOTOGRAPHY

22 UAV PHOTOGRAPHY Features: Small format camera, mounted on small un-manned aircraft Pros: Easy to mobilise Low cost equipment High resolution available, typically 2 to 5 cm Automatic software can build 3D surface models Cons: Short sortie duration, typically supporting 1 to 2 km 2 per day capture More problematic (less safe) over urban areas Uncertain DGCA permission process.

23 AIRBORNE LIDAR Aircraft based measuring laser, with GPS/IMU positioning

24 AIRBORNE LIDAR Defines terrain under vegetation and all above-ground features

25 AIRBORNE LIDAR Features: Aircraft based (helicopter or fixed-wing) Laser defining surface with many points per square metre (1 to 60 pt/m 2 ) Often operated with aerial camera Pros: Very dense definition of terrain and everything on it Large resource in India to process data Cons: Lacks richness of imagery to define non-spatial boundaries Poor dataset to show landholders to identify boundaries Requires DGCA/DRI security permits (takes 2 to 3+ months) Mobilisation costs make it less efficient for small areas.

26 UAV LIDAR Features: Small format LiDAR mounted on small un-manned aircraft Pros: Easy to mobilise Mid cost equipment (US$100,000 upwards) Sensors and platforms improving quickly Cons: Lacks richness of imagery to define non-spatial boundaries Poor dataset to show landholders to identify boundaries Short sortie duration, typically supporting 1 to 2 km 2 per day capture More problematic (less safe) over urban areas Uncertain DGCA permission process Sensors are un-insurable: $100,000 sensor in platform prone to crash.

27 TERRESTRIAL LIDAR (VEHICLE)

28 TERRESTRIAL LIDAR (VEHICLE) Features: Vehicle based (usually car but also boat, train, rickshaw, trolley, backpack) Laser defining surface with many points (50 to pt/m 2 ) Often operated with camera (to add what to the LiDAR s where ) Pros: No permits required Acquisition at vehicle speed Very efficient means of defining roadside boundaries Cons: Accuracy deteriorates in urban canyons (GCPs can assist) Boundaries limited to those visible from roadway (or other platform).

29 Maintaining Property Database

30 MAINTAINING PROPERTY DATABASE Two Main Approaches: 1. Procedural Maintenance a. Implement systems driven by permit applications b. Send surveyors out to record reported property change c. lowest cost (driven by procedure, not actuals) d. but doesn t detect unreported / illegal changes 2. Change Detection Service a. Collect Regular (annual?) imagery Satellite generally sufficient b. Automatic and/or Manual Change Detection processes c. Detect change, and send surveyors out to record property change d. Added benefit of updating property tax base.

31 CHANGE DETECTION SERVICE Sample Reports 2 epochs of WV3 imagery Automatic change detection Semi-automatic documentation

32 CHANGE DETECTION SERVICE Sample Reports 2 epochs of WV3 imagery Automatic change detection Semi-automatic documentation

33 IN CLOSING Offer Optimal DILRMP Solution: 1. Aerial photography Most efficient overall technology Rigorous, auditable, useable 2. Field Survey completion 3. Maintain Changes with Procedures 4. Reinforced with Change Detection Easy gap filling using AP as control Simple and necessary but fallible Maintain integrity of investment Additional taxation benefits