HAPEX SAHEL Information System

A joint project between LERTS, ORSTOM and CNES

Help on GRID

Most ground measurements involve point locations. These are labeled 'STATION's. Investigators often have their own naming system (e.g. EPSAT station number). Consequently, for ease of use, HSIS has adopted an identification system similar to that of FIFE Information System: namely 'GRID_ID'.

For example take the station with the location (2 30'83" E, 13 32'10" N). In decimal notation the location would be (2.513833 E, 13.535 N). The GRID_ID would then be 5153, it corresponds to tenth and hundredth of longitude and latitude (decimal). It means that all stations with a GRID_ID of xxyy will be within a square whose limits are 2.xx E and 2.xx99... E and 13.yy N and 13.yy99... N.

Since there can be several stations within one GRID_ID, a station is also given an order number, the GRID_ORDER. Each pair (GRID_ID, GRID_ORDER) designates a station with a unique identifier.

Example
-------

All of the stations of the grid cell 5153:

        GRID_ID GRID_ORDER LATITUDE      LONGITUDE
        ------- ---------- ------------- ------------
        5153    1          13.5350000000 2.5138000000
        5153    2          13.5333333333 2.5166666667
        5153    3          13.5333333333 2.5166666667
        5153    4          13.5350000000 2.5138333333

Additional Characteristics :

• A data type extension (ex. IRT = InfraRed Thermometer, BMP = Biomass Plot, etc.)
• The Super Site (S= South, CE = East Central, CW = West Central), if relevant.
• The station code given by the investigator.
• The name of the station.

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This page was updated September 29, 1995 bby T.Valero & J.C.Meunier.