[geomesa-users] problem with Geomesa SparkSQL function st_area

[邓鹏 <victordeng@xxxxxxxxxx>]

Hello,

    I am new to geomesa and recently I am researching on geo-bigdata, I have some problems with geomesa-spark. The problem is, when I use SparkSQL function st_area (https://www.geomesa.org/documentation/user/spark/sparksql_functions.html?highlight=st_area#st-area) to calculate the area of a geometry(for example a lake), the result I get is so small like 1.23e-7, I find that the unit seems to be degree^2 but not meter^2. 

    I ingested the data into geomesa accumulo with EPSG:4326, actually it has no projection, so I tried to find a way to project the data to a specific Projection Coordinate System like EPSG:4326 before calculating area, but I dont't find one.

    I also found a projectFrom function in geomesa convert transformation on geomesa documentation web page(https://www.geomesa.org/documentation/user/convert/function_usage.html?highlight=epsg#projectfrom), it says GeoMesa only supports EPSG:4326, so geometries must be transformed when ingesting from another CRS, so projection before ingesting may not work.

    Is the a way to project data so that I can get the area with the correct unit meter^2. Any help will be so appreciated.

    Thank you!

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Victor

School of Resource and Environmental Sciences, Wuhan University

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