Site mapping techniques for agricultural land
Data available for whole farm planning
In the first instance data may be assembled and assigned to broad information classes this gives an overview with regard to the data currently available and permits a proper appraisal of requirements with regard to data collection.
Broad subject areas related to farm planning are :
- Vegetation
- Soil
- Climate
- Land use
- Land systems
- Land capability
- Fauna habitat
- Hydrology
- Geology
- Administrative controls.
Where ever possible historical data should be collected so that the impact of certain farm practices may be established by analysis changes in the natural environment both with in the area farmed and the surrounding areas.
Data collection
After carefully analyzing the data currently available and considering the purposes of the project, a data collection program is developed.
Data collected typically includes :
- Maps Reports
- Photographs
- Imagery
- Ground control
- Data from specialized surveys
The data gathered may be in the form of point source data such as bore hole information transect data such as for conductivity measurements or grid based data collection of original data should be undertaken according to guidelines which take the account the nature of the analysis and the statistical take to be applied to the data to give a measure of the accuracy of the results.
Accuracy of the data
The precision required of the data for large scale mapping is high and must be consistently high for all data sets used in the analysis often data from different sources with varying accuracy are brought together over a study area and conclusion are made based on an inappropriate meaning of data sets.
Before data collection the accuracy requirements must be determined and only data collected at this level of precision or higher should be used data should never be compiled at a smaller scale than the final map product required.
Data collection and analysis
Where ever possible it is prefer able to use existing data and to carry out a limited field checking process which take the accuracy of the existing data .it is also necessary to determine whether or not the various data sets are able to be successfully and property integrated
it is useful to recognize natural sub means areas of the farms based on the simarliarty of measured values of a selected variables depending on the criteria adopted this allows management plans to be constructed in harmony with the natural boundaries typical variables used to define sub areas are soil type slope and vegetation cover.
Once data has been assembled assessed and digitized analysis using a computer begins the analysis looks at data set in turn and determine the information that the can be boundaries and with what accuracy it is possible to then look at relationships between data sets.
The transformation of data in to useful information may establish the existence of areas requiring the collection of additional data.
For the purpose of analyzing the physical factors affecting whole farm planning the following data set may be considered.
Digital elevation model of area can be derived from grid placed over a topographic map or from controlled aerial photographs the DERM can be draped with other map thematic information such as land use.
Insolation overlay showing amount of sun light reaching an area using an image analysis system the sun angle can be altered to simulate the isolation for the four seasons .
Aspect overlay can be produced from the topographic data using image analysis .
Slope overlay derived from the topographic data.
Topographic over lay can be used to relate other thematic information to height at selected coordinated.
