ikonosdata

IKONOS DATA IN MAP MAKING A

CASE STUDY

M.V.BHAT, O.P.TRIPATHI, P.K.DAS &

B.TRIPATHY

Survey Training Institute, Survey of India

Hyderabad –

500 039.

e-mail : surtrain@hd2.dot.net.in

INTRODUCTION

The ground survey on blank Plane Table Section was the initial challenge for a land Surveyor to produce

topographical map. The photogrammetry technology brought a metamorphic change in map making activities.

This technology enabled drawing of blue print of map in office itself with minimum ground control points (GCPs).

The final map can take shape after the ground truth of the blue print drawn. The input in the technology is the

aerial photograph.The map updating with a view to bring the new edition is a periodic phenomenon. Besides, the

same area may need to be mapped in different scale for specific purposes. A pool of aerial photograph of the same

area taken for primary mapping may not be useful for aforesaid mapping owing to the scale constraint of the

photography as well as lack of details of the area which has come up after the date of the photography. The

solution is fresh photography for each purpose that is very cumbersome and inconvenient due to various reasons.

Under this circumstances the map maker was always looking forward to use of Imagery in place of photographs

which could offer a better solution as revisit of satellite to the same area is very frequent.

We did not get a heading in this direction of map making using Imagery because the satellite cameras are not

able to provide us the adequate radiometric and geometric resolution. Now that INKONOS is able to provide us 1

metre resolution panchromatic data with 11 bit radiometric resolution, we can look forward to use the same and

envisage another metamorphic change in map making activities. As a map maker, we can now serve our users

with maps containing updated information of the terrain as it is

on date, by exploring the IKONOS DATA.

This paper deals with a case study in exploring the ways and means to use the IKONOS data for map

making. Necessary comparison for accuracy and other parametres

that this imagery can yield have been critically

evaluated.

2.0 SPECIFICTION OF IKONOS DATA

Spatial Resolution

1 metre panchromatic 4 metres multi spectral

Spectral Resolution

0.45 to 0.90 Micron

Panchromatic # 1 Blue 0.45 –

0.52

Multi spectral

# 2 Green 0.52 –

0.60

# 3 Red 0.63 –

0.69

#4 Near IR 0.76 –

0.90

Radiometric Resolution

11 bit data

Temporal Resolution

2.9 days at 1m resolution

1.5 days at 1.5m resolution

3.0 ABOUT IKONOS PRODUCT

The IKONOS images are available in standard map projection. Different products have different

geometric characteristic both stereo and non-stereo imagery delivered also includes Image Geometry Model (IGM),

which precisely describe the sensor Geometry

Non-stereo Imagery delivered are of two types

Geo Product

Geo ortho Kit

Geo Product:

This is the Geo rectified Product commonly knows as “

Map Oriented”. Geo images are

rectified to a reference elevation model determined from a global database. Though the imagery is available in an easy

to use map projection the horizontal accuracy is limited by terrain displacement, which at times is in hundreds of

metres due to low elevation angle of Geo images. This Geo images are recommended only for visual information and

not for map making.

Geo ortho Kit:

This product consist of a high resolution Geo images taken with high sensor elevation angles

and precise image Geometry and an Image Geometry Model (IGM) digital file. From this imagery an accurate ortho-

rectified image can be created carrying out digital ortho-rectification with the help of IGM together with the Digital

Elevation Model (DEM) and the ground control points (GCPs). That is why this product is best suited for mapmaking

activities. Since IGM provides the complete and accurate sensor

geometry, the metric accuracy of the final ortho

rectified image is limited only by the accuracy of the DEM and GCPs. This product is available in 1 metre black and

white, 1 metre colour or 4 metre

multispectral.

Apart from the products described, the Space Imaging and Veridian developed many New Image Base Product

designed in varied resolutions and formats, specifically for government and military users.

4.0 S/W USED FOR ORTHO-RECTIFICATION & FEATURE EXTRACTION

There are few Digital Photogrammetric S/W package which provide the facilities for ortho-rectification of

IKONOS Geo Ortho Kit product viz. ERDAS

IMAGINE Ortho BASE, Z/1 Imaging Image Station ortho Pro

PCI. Geomatics Geomatica

, Ortho Engine

etc., In this case study the ERDAS

IMAGINE Ortho-BASE has been

used.

WORK FLOW: -

The workflows of map-making from IKONOS data as envisaged and followed is as under: -

The vector data from the rectified Imagery was collected using appropriate vector tools of the software as per

prescribed data model in scale 1:10,000. The same area was also

plotted in analogue photogrammetric plotter by

conventional method in the same scale. Both the Outputs were compared and found to agree fairly except those came

up after photography.

Row

Point ID

X Input

Y Input

X Ref.

Y Ref.

GCP #1

GCP #2

GCP #3

GCP #4

GCP #7

GCP#12

GCP#13

GCP#14

GCP#15

GCP#18

GCP#19

GCP#21

GCP#22

GCP#23

234420.720

233330.806

233875.580

233818.439

234694.927

237906.079

239984.314

240020.972

242054.767

240465.753

236688.411

232065.661

232447.777

236080.617

1921606.972

1917818.597

1916137.098

1916145.638

1914767.495

1919127.196

1916313.120

1916365.611

1918773.761

1922864.069

1922051.849

1921443.393

1923189.448

1924649.817

234460.475

233382.073

233934.588

233877.651

234762.696

237957.833

240049.529

240085.790

242111.084

240505.721

236728.411

232105.957

232482.049

236109.711

1921594.829

1917809.263

1916128.217

1916137.711

1914761.893

1919112.255

1916300.129

1916353.250

1918757.639

1922841.843

1922035.659

1921433.337

1923176.872

1924633.233

RMS ERROR: [X]=1.1206 [Y]=1.0904

total: 1.5635

5.0 PROCEDURE FOLLOWED

The raw IKONOS data including IGM data of the area of case study

was Ortho-rectified using the DEM of the area

(created from old map data) controlled by ground control points (GCPs) obtained by differential GPS technique.

The RMS error together with the residuals in carrying out the rectification is as below:-

GCP RESIDUALS

RAW IKONOS IMAGERY

GCPS THROUGH DGPS

DEM

ORTHO RECTIFIED

IMAGERY

VECTOR DATA CAPTURE

FIELD VERIFICATION

DATA VALIDATION

FINAL MAP PREPARATION

7.0 FUTURE SCOPE

The use of Stereo-Imagery of IKONOS needs to be exploited for creation of DTDB of topo-maps together with

the contours. Then only the real goal will be realized.