500
Let’s consider the method of estimating the proper season of
aerial photography. In the desert the maximum optical contrast between the
natural objects is observed in spring. So in sand deserts spring is the
most suitable season of aerial photography. The beginning and end of this
period have been estimated on spectral reflectance data and phenology of
indicator plants.
As indicator plants have been taken Haloxylon pevsicnm and
Carex physedes. In the phenological chart (Fig. 3) the beginning of the
vegetative stage of Haloxylon persicum is shown, with intervals of 10 days.
To estimate the beginning of the proper season of aerial photography 10
days should be added to the isophene.
The second phenological chart (Fig. 3) shows the approach of
Carex physedes withering. Simultaneously all other ephemeres and
ephemeroids wither up.
Aerial camera is the most widely used remote sensor in the
desert zone. It is obvious that another remote sensor can be used here.
Mathematical treatment of data has shown spectral bands in which the greatest
number of objects can be identified in aerial photos. The spectral bands
providing the maximal contrast are the following: 1. in the sandy desert
400 - 525 nm and 600 - 675 nm, 2. in the foothill country 400 - 500 nm and
620 - 680 nm, 3. in the man - made landscape 600 - 675 nm and 750 - 850 nm.
One can suppose that using multispectral technique will give
good results by obtaining imagery in spectral bands mentioned.
LITERATURE CITED
Kol'tsov V.V. Spektrofotometricheskie kharakteristiki elementov zemnoi
poverkhnosti i ikh izmerenie dlya tsolei aerofotos”emki (Spectral
reflectance properties of landscape elements and their measurements
for aerial photography). Isaledovanie opticheskikh svoistv
prirodnykh ob”ektov i ikh aerofotograficheskogo izohrazheniya. Izd.
Nauka, L., 1970.
Kharin N.G. Lesokhozyaistvennoe deshifrirovanie aerosnimkov (Forest photo -
interpretation). Izd. Nauka, M., 1965.
Kharin N.G. Karty sezonnogo razvitiya pustynnoi rastitel'nosti
(Phenological charts of desert plants). Izvestiya AN Turkm. S.S.R.
(ser. biol.), 1966, N. 5.
Billings W.D. and R.J. Morris. Reflection of visible and infrared radiation
from leaves of different ecological groups. Am. J. Bot., 1951, Vol.
38, N. 5.
Howard J.A. The reflective foliaceous properties of tree species. Appl.
Remote Sensors in Forestry. Freiburg, 1971.
