Crop hectare estimation by means of satellite image analysis & sampling techniques
Zahra Shoari
Introduction
Agricultural estimates using remotely sensed data is a subject has been investigated and tested around the world during the last decade. In this sense it important to point out that Remote Sensing techniques do not replace traditional procedures for gathering agricultural data, considering these procedures objects and reliable. However, depending on the actual situation in each country, Remote Sensing could become a decisive element of the system.
Objective
The main objective of this project is wheat / barely identification and hectare estimation.
Project area
The project area is the GORGAN-GONBAD region of MAZANDARAN province in the north-east part of IRAN. It is one of most important areas for crop production in the country, presenting a typical intensive agricultural pattern. It is a almost flat region upto the foot of the ALBORZ mountains with soils ranging from high to regular capacity for agricultural purposes. Main crops in the region area wheat, barely and cotton being followed by second harvest corps like rice, soyabean, broad bean, potatoes, different vegetables and fruits complete the agricultural pattern in some specific area. Wheat and cotton usually are irrigated but almost all barely production is just rainfed.
Field sizes vary accordingly from approximately 20-50 ha 1-5 ha.
The project has been done in 3 phases as follow:
PHASE – I
*STRATIFICATION
Stratification is a well known procedure by which a region is divided into subarea or strata with the objective of grouping homogeneous areas, with respect to one or more specific variables. The purpose of the stratification in agricultural surveys is toe increase the precision of the sample survey estimates.
* PROJECT AREA STRATIFICATION
The stratified sampling design used in this project provides separate estimates of mean and variance for each stratum generally given a more precise estimates of these parameters for the entire population than an in the case of a random sample design for the whole area. Due to the necessity of estimating the sampling error within each stratum, attention should be given to the fact that the stratum size permits the allocation of a proper number of sample units to compute that error. The GORGAN-GONBAD area was stratified using topographic maps and Landsat MSS and TM images from different dates of the major crops growing season. Four strara were identified and delineated on the Landsat TM image.
A field trip allowed the boundary control and description:
LEGEND
STRATUM 1: correspond top the piedmont of ALBORZ mountains landuse is characterized by a high agricultural activity pattern with small to medium field size (1-10 ha). Main crops are wheat and cotton also including vegetables, fruits, potatoes etc. total area – 109700 ha
STRATUM 2 : correspond to the alluvial plain of the Gorgan river it is a large area with intensive agricultural activity. Field size varies from medium to large (5 – 25 has) being wheat and cotton almost exclusive crops during the spring season. Wheat is largely the major crop and only around villages other crops appear in smaller fields. Total area = 142200 ha.
STRATUM 3 : Correspond to the alluvial plain of Gorgan river this area presents an extensive agricultural pattern being barely the excluyent crop few wheat field are observed only where soil conditions are better. Field sizers are the largest of the region (more than 20 ha) when smaller is due to drainage channels pattern near villages. Total area = 108500
STRATUM 4 : Correspond to the alluvial plain of Gorgan river it is characterized by an intensive agricultural practice devoted mainly to summer crops (cotton). Fields size is medium to large and few winter crops are found. Total area = 20800 ha
