Our project is generating local excavation data from a local grid which we eventually want to transform from the local coordinates to real world coordinates. In this case we want to convert/translate to UTM 36 N. We are measuring ground control points at several locations in the grid.

Is there any easy-to-use tool which would allow us to transform to UTM based on a table of GCP and Local Points?

We are generally using QGIS, but I have not found a valid option for our usecase, yet.

  • 1
    Affine transformation plugin may help. – Zoltan Jan 28 '19 at 14:55

What we do is define a custom reference system for each of our survey projects.

It is worth mentioning that our local systems are always oriented towards the true north, and the origin of coordinates is some fixed point internal to the survey (we could handle false easting and northing if we do not want negative coordinates).

For example, if in our survey we have the origin of local system coordinates coinciding with the longitude -59.7 and the latitude -34.2 (we usually handle some more decimals), we use the following custom CRS:

+proj=tmerc +lat_0=-34.2 +lon_0=-59.7 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs

What we are doing is to define a transverse, tangential mercator projection centered on our fixed point.

Each survey of a project is adjusted to assume the same reference system.

When necessary, we export the layers to the reference systems requested by public bodies.

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