Comparing And Contrasting The Various Survey Methods For

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COMPARING AND CONTRASTING THE VARIOUS SURVEY METHODS FOR PROPERTY DEFINITION by David Jonas, Spatial Solutions Consultant 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. AAM India Geosmart India 2016 Acceptable Survey Methodologies 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. AAM India Geosmart India 2016 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. AAM India Geosmart India 2016 SATELLITE IMAGERY 30 cm Satellite Imagery of Delhi AAM India Geosmart India 2016 SATELLITE IMAGERY 30 cm Satellite Imagery of Delhi AAM India Geosmart India 2016 SATELLITE IMAGERY Features: • Range of platforms including Cartosat, Digital Globe, … Pros: • No mobilisation costs • Can provide the 3rd dimension with stereo coverage Cons: • Accuracy doesn’t really meet stipulated 1:1000 specifications • Low resolution makes more difficult to recognise subtle land boundaries. AAM India Geosmart India 2016 TRADITIONAL TRADITIONALAERIAL AERIALPHOTOGRAPHY PHOTOGRAPHY AAM India Geosmart India 2016 TRADITIONAL TRADITIONALAERIAL AERIALPHOTOGRAPHY PHOTOGRAPHY AAM India Geosmart India 2016 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. AAM India Geosmart India 2016 MODERN AERIAL PHOTOGRAPHY New Technology: eg. VisionMap A3 Allows wider capture per run AAM India Geosmart India 2016 MODERN AERIAL PHOTOGRAPHY VisionMap A3: Rotating Head Camera AAM India Geosmart India 2016 MODERN MODERNAERIAL AERIALPHOTOGRAPHY PHOTOGRAPHY AAM India Geosmart India 2016 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 (10,000km2 +) 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. AAM India Geosmart India 2016 ACCEPTABLE SURVEY METHODS Field Survey: • Electronic Total Station • Differential GPS 1. Accuracy Aerial Remote Sensing: • High resolution satellite imagery • Aerial Photography 2. Accessibility 3. Resolution 4. Land holder familiarity Other Methods which can be Explored • Unmanned Aerial Vehicle • Terrestrial LiDAR • Mobile LiDAR • Aerial LiDAR. AAM India Geosmart India 2016 5. Auditability 6. Permissions 7. Timeframes 8. Other Applications. COMPARING FIELD VS AERIAL Field Survey Aerial Remote Sensing Accuracy: • centimetre / decimetre • decimetre (AP) / metre (satellite) Accessibility: • Need access to, or visibility of, every property vertex • Inaccessible vertices incomplete • Need to see every property vertex from above • Vertices under trees incomplete Resolution: • Non-straight boundaries difficult • Non-straight boundaries easy Land holder familiarity • only linemap to describe boundary • Rich imagery to describe boundary AAM India Geosmart India 2016 COMPARING FIELD VS AERIAL Field Survey Aerial Remote Sensing Auditability: • No accountability of correct pointing • Pictorial archive provides audit and legal traceability Permissions: • Property owner permission to enter • DGCI/DRI permission for survey Timeframes: • Quick start-up, slow acquisition • Slow start-up, quick acquisition Resources • Limited by equipment availability • Vast photogrammetric capacity Other Applications: • Able to leave monumentation • Othos and DTM vital data layers. AAM India Geosmart India 2016 Other Mentioned Survey Methodologys UAV PHOTOGRAPHY AAM India Geosmart India 2016 UAV PHOTOGRAPHY AAM India Geosmart India 2016 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 km2 per day capture • More problematic (less safe) over urban areas • Uncertain DGCA permission process. AAM India Geosmart India 2016 AIRBORNE LIDAR Aircraft based measuring laser, with GPS/IMU positioning AAM India Geosmart India 2016 AIRBORNE LIDAR Defines terrain under vegetation and all above-ground features AAM India Geosmart India 2016 AIRBORNE LIDAR Features: • Aircraft based (helicopter or fixed-wing) • Laser defining surface with many points per square metre (1 to 60 pt/m2) • 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. AAM India Geosmart India 2016 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 km2 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 . AAM India Geosmart India 2016 TERRESTRIAL LIDAR (VEHICLE) AAM India Geosmart India 2016 TERRESTRIAL LIDAR (VEHICLE) Features: • Vehicle based (usually car but also boat, train, rickshaw, trolley, backpack) • Laser defining surface with many points (50 to 1000+ pt/m2) • 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). AAM India Geosmart India 2016 Maintaining Property Database 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. AAM India Geosmart India 2016 CHANGE DETECTION SERVICE Sample Reports 2 epochs of WV3 imagery Automatic change detection Semi-automatic documentation AAM India Geosmart India 2016 CHANGE DETECTION SERVICE Sample Reports 2 epochs of WV3 imagery Automatic change detection Semi-automatic documentation AAM India Geosmart India 2016 IN CLOSING Offer Optimal DILRMP Solution: 1. Aerial photography  Most efficient overall technology  Rigorous, auditable, useable 2. Field Survey completion  Easy gap filling using AP as control 3. Maintain Changes with Procedures  Simple and necessary but fallible 4. Reinforced with Change Detection  Maintain integrity of investment  Additional taxation benefits AAM India Geosmart India 2016