Ground Truth Database with Portable GPS for Education
4. Functions
4.1 Geometric Correction By the recent innovation of GPS technology, many types of GPS are available. In this study a handy type GPS named "GERMIN GPS38J" are selected because
of (a) valid accuracy of 20-30 which is effective for LANDSAT-TM image identification requiring at least 30m positioning accuracy, and (b) portability. FIG-2 shows a time series average accuracy changes for 1,000 seconds. From this figure, GPS positioning requires about 10 minutes for each point in order to get 30nm accuracy in horizontal plane.
Figure 2 Handy GPS Positioning Accuracy (Sequential Average)
Figure 3 Classification Hiearchy
GCP should be distributed equally into the whole image of study area. Incase enough GCP can not acquired from the field survey, existing topomap will be used foradditional GCPs. In this system, affine,2nd order and 3rd order transformation formula for geometric correction are supported. Moreover, navigation function is included in this system.
4.2 Ground Truth and Classification
Handy GPS and Digital Camera are for gathering Ground Truth (GT) classification is instructed as follows:
Firstly three different types of clustering process are carried out. Macro clustering make rough classification with 6 to 8 categories, and meso clustering has about 100 categories. A hierarchy of relationship between categories in the different class resolution image will be established, then field investigation will be made for the categories in the micro scale classification. Pictures of the GT are recorded with the position information.
It is difficult to take GT for all micro categories, some typical micro categories are selected from meso categories, and checked. Ana a typical reflectance characteristics is selected from 9 pixels around the target GT including itself because the positioning accuracy to expected around 30m. The final classification will be done using existing meso classification, or supervised classification using the GT databaset. Even it is the same category-such as paddy field -in the different image, season, or region, the radiometric characteristics are different and it can be recognized from the GT database.
In case no information are given onto the image to be processed, some adequate land cover categories are suggested using a key of reflection characteristics from the GT database. By the standarization of the GT database, data acquired form independent field investigation can be accumulated and utilized for the training and education purpose.
2. Discussion
The developed system has 3 functions : (a) geometric correction, (b) classification, and (c) database management. These are all fundamental procedure for remote sensing image interpretation and processing, so that instruction these subject to beginners is also quite points of user interface are (1) Visible, 9s) more mouse operation, less key input, (3) fw instruction and more help and (4) popular and inexpensive equipment. The system is still under the trial version and improvement should be made according to the users requests.
References
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TOMITAMK and MATSUYAMA, H(1996) Development and investing of Semi-Differenctial GPS, Theory and Applications of GIS, Vol 14, No. 2, pp. 15-27.
- TSUCIYA, J. and TSUJI, H. (1995) GPS Sikuro-no kiso, survey Association of Japan (Nihon Sokuyo-kyokai)
- Japan Associations on Remote Sensing (1993) Remote Sensing Note.
