Updating and application of DTM on Violent Hill-Slope Land Development
Hain-Hsing Cheng 1, Kai-Huri Lin2 ,Wen-Fu Chen3
1 Graduate Student Dept. of Soil and Water conservation.,
National chung- hsing Univ., Tai-chung, 402, Taiwan
2 Project Manager of HILTRON TECH, Inc. f3,3 aly,
3 In;# 194 Chung-Shan Rd,Sec.4.Tai- chung,402,Taiwan
3 Professor, Dep. Of Soil and water conservation,
National Chung-Hsing Univ., Tai-chung ,402, Taiwan
Keyword: Digital Terrain Model (DTM);Hill-slope Land Development
Abstract
Due to violent development of a hill-slope land, there would be tremendous change on terrain and land features. The exited DTM data of that area should be out of date and not be usable because of the changing of terrain. For feature usage of the DTM data after large amount of exploit, the update DTM data is strongly required. Although there are many methods could be used to produce a new DTM data, such as map digitizing, field survey, photogrammetry and remote sensing, those work often takes a lot of expenditure, time and labor. Focusing on a partial change on large area, the traditional methods do not seem to be economical and cannot rapidly achieve new DTM data. The objective of this study is to compare the satellite images of different periods and then modify the major change by manual digitizing. We expatiated hoe we used AutoCAD to readily digitizing the changed area with recent topographic map to achieve the contours. Then ARC/INFO was used to proceed data transform,interpolate,....etc. furthermore, the newly produced DTM data was replaced to that on the changed area to achieve new DTM data. Due to the rapid achievement, this approach can be applied to many fields. In this study we will also introduce some possible applications.
Introduction
Due to rapid economic development and population explosion recently in Taiwan, So for social milieu development required, many of the big non-agriculture hill-slope land violent developing such as esplanade, golf course and freeway etc., there would be tremendous change on terrain and land features. Because of violent change , the DTM data of whole area before developing have not useable in changing part and strongly required of updating to correspond with actually application. There are many methods can produce new DTM data, such as map digitizing, field surveying, photogrammetry and remote sensing etc.
(1,2,3,4) ,but they often need to spend a lot of human power and expenditure. Focusing on a partial Change on a large area, the traditional method don't seem to be economical and can't rapidly achieve new DTM data in development area. So this study is to use Arc/Info and AutoCAD that can fist digitizing on computer screen to select the newer photographic base map of development area in watershed. Digitize its contours, boundary and transform the data format. First, update the DTM data in developing area next merge the total area DTM data and complete the new DTM.
Study Area Description
This study area includes Sinpu and Guansi towns of Hsin-Chu County and it is 208 km2 in area. These is a hydrologic observing station at the upstream of Fon-san Watershed. The coordinates of this study area include TM2(E, N)=(255160,2752960)at upper left corner and TM2(E, N)=278800, 2734920) at lower right corner. The elevation is from 48 meters to 1330 meter. Terrance is incised by rivers to become rough and with tributary.
The main stream of Fon-San stream and its tributary- Shau-Li stream are flatter than any other tributaries. Most roads are constructed along the river valleys. This study area are covered by hardwood, Taiwan Acacia forest, grass, tea garden, rice field and naked soil. There are eight Golf courses, Liu-Fu village, Window of China, the 2nd northern freeway and 4 mining fields of limestone.
(5)
Selection of the sites
According to 40m-resolution DTM of Taiwan to measure the change of hill- slope land, we can not measure the smaller developed area and variant of volume. Oppositely, apply present precision DTM to detect development of large area hill-slope land and coordinate with remote sensing data which covers large are, have periodicity and are covers to get and establish GIS database to combine GIS and RS detecting big area land use change can be arrived. That's the reason why we choose the developed hill-slope land above the 50-100 hectare, such as golf course, the 2nd northern freeway, mining field and large playground.
(5)
Study Material
Satellite images of SPOT,40m- resolution DTM, photographic base map 1/5000 scale, TM2, total 52.
Procedure and methods
1. Watershed DTM Updating after development
The detailed steps and methods is as following:
-
Digitize the boundary of the developed area and the contours inside that area.
- Transforming data format
- Getting TIN
- Transforming the data formats of LATTICE and TIN
- Subsetting the DTM of watershed
- Deleting the DTM data of the developed area in the watershed
- Merging
The detailed updated DTM flow chart shows in Figure 1.
2. Compare the DTM before and after the development
The DTM show tremendous difference before and after the development. It was Shown figure 2 and3.
The differences also shoe in shading method, just as in figure 4 and 5.
The higher the DTM resolution and precision is the greater the difference will be.
(6,7,8)
