Analysis of interpretation properties of forest lands
on various scale TM imagery1
Li Jiquan
Research Institute of Forest Resource information Techniques,
Chinese Academy of forestry
Abstract
This is paper described the radiation between TM image scales and its interpretation properties of forest lands and purposed optimal TM image scale for forest survey in "Three north Shelter forest Region".
General situation of study area and applied information source
Kangbao county is located at the north part of Zhangjiakou prefecture, Hebei province. Its geographical position is 41 25'-42 09 N and 1114 11 114 57 'E belong to the south east part of Mongolian Plateau and the elevation is from 1300 m to 1700 m the annual precipitation in 350 mm and its is very windy and dusty Kangbao County is a transit region from aired steeple to forest grasslands and the vegetation type is simple [1] is no natural forest in Kangbao County and small pieces of artificial forest are scattered nearby the villages and small towns however the covering area of arm land wind break forest network is extensive LANDSAT 5 false color composite TM image scale 1:1000,000 1:200,000 and 1:500,000 imaged in 8th Sep 1897 were employed in this research.
Forest interpretation and area measurement on TM imagery
- The timing of TM image employed in the research is very opportune by this time most crops have been harvested The outlines of forest lands and windbreak forest network are clearly discernible on TM images which affords is a favourable conditions to improve the forest interpretation precision(FRITP).The interpretation keys are as follows:
forest lands----with obvious regular shape. The tone on 1:100,000 scaled TM image is fresh and light red colour; and on 1:200,000 and 1:500,000 scaled TM images is dark red color. Windbreak forest network----with clear netted and belt shape. The tone on 1:100,000 scaled TM images is red color and dark red color appears on 1:200,000 and 1:500,00 scaled TM images .
Visual interpretation and plot delineation of forest lands and wind break forest network were carried out respectively on 1;100,000 and 1:200.000 as well as 1:500.000 scaled TM images according to the records obtained during fields survey in Kangbao County and relevant specialized maps and materials as reference.
- The 'KP-90 N" model digital planimeter was employed to measure the area of forest lands To counter of some forest area smaller than the minimum measurable area of planimeter (ie 10 ha. On 1:100.000 scaled interpretation map) the following method was adopted to solve the above problem i.e several adjacent small piece forests were constituted in to larger plot for area measurement, and a DOT-GRID with dense dots was employed to measure the weight of every small piece forest than their actual area could be calculated respectively.
Fig.1 TM image on the scale of 1:100,000
Fig.2 TM image on the scale of 1:200,000
Fig.3 TM image on the scale of 1:500,000
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1. Mr Li Yingguo and Ms. Wu. Honggan Bai Suhua (Research Institute of Resources Information, Chinese Academy of Forestry) partly participated in this research work.
