ETM data （Aug.

1999）

statistics data of 25 sampling sites with size of 4m by 4m and 1:250

000 scale DEM data. and digitized 1 to 100

000 scale distribution map of endangered rare plants are used to study the vertical and horizontal distribution patterns. Endangered rare plants group information was extracted by using Masking Principal component transformation and Hue adjust （MPH） technique. And then the feature imagery was merged with DEM data to produce a virtual reality 3-D imagery to see the differences of rare plant in relation to topographical and soil enviroment. The soil type is affected mainly by topography in this desert area. An analysis model was established to organize different data set. The endangered rare plants in West Ordos Plateau

mainly Tetraena mongolica

Helianthemum soongolicum

Reaumuria trigyna

Reaumuria soongorica

Potaninia mongolica

Ammopiptanthus mongolicus and they are evolved from Tertiary

are for a long time regarded as environment change diagnostic indicators. They also have very precious value to study environmental evolution

plant diversity and geography in global scale. These plants have also played a very important role in maintaining ecosystem in terms of preventing desertification. The vegetation spectral feature ranging from 0.63 to 1.1 μm is called reflectance “shoulder”

which is the spectral character for NDVI

BIOMASS and NPP calculations. In the study we used TM and ETM blue bands（ 0.63—0.69μm） and near infrared band4 （0.775—0.90μm）. To differentiate spectral features of rare plant groups the MPH technique was used. The technique was implemented in two steps. Masking

and Principal component transformation. Firstly

water bodies and some alluvium were masked out from ETM 1

2

3

4

5

7 bands

which could reduce the variance features for next step processing. Principal component transformation algorithm had the function that can compress the common features into first component. In order to get rid of terrain illumination （mainly BRDF/ALBEDO）from all imported bands

we used the PCA compress function to reduce terrain illumination. After Principal Component Analysis the first component contained most of common BRDF/ALBEDO information. Three MPH resultants

MPH 2

MPH 3and MPH 4 were selected and combined to make a color composite. The method employed in the study can be widely used as a monitorying tool for the future decision making in protection of the endangered rare plants.