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COMPARING AND CONTRASTING THE VARIOUS SURVEY METHODS FOR

PROPERTY DEFINITION

by David Jonas, Spatial Solutions Consultant

AAM India Geosmart India 2016

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.

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.


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.


SATELLITE IMAGERY

30 cm

Satellite

Imagery

of Delhi


SATELLITE IMAGERY

30 cm

Satellite

Imagery

of Delhi

SATELLITE IMAGERY


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.


TRADITIONAL AERIAL PHOTOGRAPHY TRADITIONAL AERIAL PHOTOGRAPHY


TRADITIONAL AERIAL PHOTOGRAPHY TRADITIONAL AERIAL PHOTOGRAPHY


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.


MODERN AERIAL PHOTOGRAPHY

New Technology: eg. VisionMap A3 Allows wider capture per run



VisionMap A3: Rotating Head Camera


MODERN AERIAL PHOTOGRAPHY 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.


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.


COMPARING FIELD VS AERIAL

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

Field Survey 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


COMPARING FIELD VS AERIAL

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

Field Survey 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.

Other Mentioned Survey Methodologys


UAV PHOTOGRAPHY


UAV PHOTOGRAPHY


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.


AIRBORNE LIDAR

Aircraft based measuring laser, with GPS/IMU positioning


AIRBORNE LIDAR

Defines terrain under vegetation and all above-ground features


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.


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 .


TERRESTRIAL LIDAR (VEHICLE)


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).

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.


CHANGE DETECTION SERVICE

Sample Reports

2 epochs of WV3 imagery

Automatic change detection

Semi-automatic documentation


CHANGE DETECTION SERVICE

Sample Reports

2 epochs of WV3 imagery

Automatic change detection

Semi-automatic documentation


IN CLOSING

Offer Optimal DILRMP Solution:

1. Aerial photography

2. Field Survey completion

3. Maintain Changes with Procedures

4. Reinforced with Change Detection

Most efficient overall technology

Rigorous, auditable, useable

Easy gap filling using AP as control

Simple and necessary but fallible

Maintain integrity of investment

Additional taxation benefits

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COMPARING AND CONTRASTING THE VARIOUS SURVEY METHODS …geosmartindia.net/presentations/gis-surveying-mapping-land... · COMPARING AND CONTRASTING THE VARIOUS SURVEY METHODS FOR PROPERTY