Lunar Digital Elevation Model Generation

using Chandrayaan-1

Terrain Mapping Camera (TMC)

K. SURESH

HIGH RESOLUTION DATA PROCESSING DIVISION

SIGNAL AND IMAGE PROCESSING GROUP

Introduction

Prime objective of Terrain Mapping Camera (TMC)

High resolution 3D mapping of topographic features

Triplet Imaging (Fore, Aft and Nadir)

B/H Ratio is 1

DEM Generation Combinations

Nadir-Aft

Nadir-Fore

Fore-Aft

Nadir-Fore-Aft

Envisaged to generate Higher Level Products (DEM, Ortho Image and Lunar Atlas) at SAC, Payload Operations Center (POC)

Indigenously Designed and Developed Software Package called LDEM for Fully Automatic DEM and Ortho Image Generation

Functions of POC @ SAC

POC focuses on

Higher Levels of processing for the science data

Planning of payload operations

Performance assessment of the payload

Payload calibration and Data Preparation

POCs are co-located with the

Laboratory/offices of Instrument designers/PIs and

Support the required infrastructure for processing storage and network connection

TMC Viewing Geometry

FOV :across track : ± 5.7º

along track : ± 25º

Fore to Aft : 60.3s (56 pixels shift due to moon rotation)

Swath 20Km

Chandrayaan-1 TMC Triplet Imagery

FORE NADIR AFT

DEM Generation Options

DEM Generation Combinations

Nadir-Aft

Nadir-Fore

Fore-Aft

Nadir-Fore-Aft

DEM Posting

25 Meter – First Version

10 Meter – Second Version

5 Meter - Experimentation

DEM Generation Overview

Reference Data Sets

Clementine Equatorial, North and South Pole Mosaic

ULCN Points for Height Reference

LRO WAC Equatorial, North and South Pole

Mosaic

LRO LOLA Points for Height Reference

Input Data Sets

Level-1 Product (Radiometrically

corrected)

Orbit, Attitude and Time

Ancillary Information (LBR and SPM)

Output

Equatorial Data in Seleno graphic Coordinates

North and South Pole Data in Polar Stereographic Projection

Moon Spheroid Datum (Mean Radius 1738km)

DEM in 25m and 10m Postings

Ortho Image in 5m Resolution

Format

GeoTiff (Classic and BigTiff)

DEM Generation

Full Strip DEM and Ortho Image Generation (Length:600km to 1800km)

Overlap Computation

Overlap b/w Fore, Aft and Nadir using Physical Sensor Model.

Imaging Model

Precise mapping between image and ground using

Sensor parameters (focal plane geometry in terms of alignment angles),

Platform parameters (orbit and attitude of the spacecraft) and

Scene parameters (terrain related information like datum, elevation)

Lunar Control Point (LCP) Identification

Same Point Identification on Fore, Aft and Nadir with respect to Reference.

Normally 25 to 50 LCPs are identified for each orbit depending on the length of the pass/strip

Space Resection

LCPs are used in space resection model to derive the refinement parameters.

DEM Generation …

Hierarchical Image Matching (HIM)

Generating dense conjugate points across the images of TMC i.e. the Fore, Aft and Nadir. Nadir as Reference Image.

Space Intersection – Irregular DEM

Object space coordinates are computed for irregularly spaced conjugate points generated using HIM technique .

Regular DEM Generation

Constrained Interpolation

No Height Value (-20000)

Grid and Ortho Image Generation

Ortho Rectification of Nadir Image

LDEM Results Pre and Post (100km) are Shown Below…

Output Visualizations and DEM Comparisons

DEM and Ortho Image

Surface Reconstruction using 10m DEM

Filtering Height Values

DEM 2.5D View with Ortho Image

DEM 2.5D View with Ortho Image

DOP:15-12-2008 Imaging Orbit:437

25m Color Coded DEM

10m Color Coded DEM Difference

Color Coded DEM

Frequency

Height (-17.5m to 10m)

Difference DEM Histogram

25m Color Coded DEM

10m Color Coded DEM

DOP:15-12-2008 Imaging Orbit:437

Comparison of DEMs (25m,10m and 5m)

25m DEM 2.5D View

10m DEM 2.5D View 5m DEM

2.5D View

DEM and Ortho Image Evaluation

DEM Visualization 2.5D Anaglyph

DEM Visualization 2.5D Anaglyph

Thank You