# Set coordinate value¶

New in version 7.0.0.

Set component(s) of a coordinate to a fixed value.

 Alias set Domain 4D Input type Any Output type Any

This operations allows for components of coordinates to be set to a fixed value. This may be useful in pipeline when a step requires some component, typically an elevation or a date, to be set to a fixed value.

## Example¶

In the ETRS89 to Dutch RD with NAP height transformation, the used ellipsoidal height for the Helmert transformation is not the NAP height, but the height is set to 0 m. This is an unconventional trick to get the same results as when the effect of the Helmert transformation is included in the horizontal NTv2 grid. For the forward transformation from ETRS89 to RD with NAP height, we need to set the ellipsoidal ETRS89 height for the Helmert transformation to the equivalent of 0 m NAP. This is 43 m for the centre of the Netherlands and this value can be used as an approximation elsewhere (the effect of this approximation is below 1 mm for the horizontal coordinates, in an area up to hundreds of km outside the Netherlands).

The +proj=set +v_3=0 close to the end of the pipeline is to make it usable in the reverse direction.

\$ cct -t 0 -d 4 +proj=pipeline \
+step +proj=axisswap +order=2,1 \
+step +proj=vgridshift +grids=nlgeo2018.gtx \
+step +proj=push +v_3 \
+step +proj=set +v_3=43 \
+step +proj=cart +ellps=GRS80 \
+step +proj=helmert +x=-565.7346 +y=-50.4058 +z=-465.2895 +rx=-0.395023 +ry=0.330776 +rz=-1.876073 +s=-4.07242 +convention=coordinate_frame +exact \
+step +proj=cart +inv +ellps=bessel \
+step +proj=hgridshift +inv +grids=rdcorr2018.gsb,null \
+step +proj=sterea +lat_0=52.156160556 +lon_0=5.387638889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel \
+step +proj=set +v_3=0 \
+step +proj=pop +v_3


## Parameters¶

+v_1=value

Set the first coordinate component to the specified value

+v_2=value

Set the second coordinate component to the specified value

+v_3=value

Set the third coordinate component to the specified value

+v_4=value

Set the fourth coordinate component to the specified value