Technical Tip: Distorting Snapplot to Improve Display

30 September 2009

Snapplot is a component of the programme SNAP (Survey Network Adjustment Package). Snapplot provides a map view of geodetic stations and observations, as well as adjustment data and results.

When stations in a geodetic network are close together, it is often useful to modify the displayed positions of these stations in Snapplot to improve clarity.

In Figure 1 above, taken from Snapplot, there are two areas of overlapping text (red boxes), indicating there are marks in close proximity to each other.

To better display these marks and the associated observations the 'offset a station' technique can be used. To do this, hold down ‘Shift’ and ‘Ctrl’ and drag the station to the desired position by holding down the left mouse button.

This produces the distorted diagram in Figure 2 above. As well as being useful for display and printing purposes, the station offsetting process has identified a weakness in the network, an unchecked line between BK4C and BK9C.

To return a station to its original position, hold down ‘Shift’ and ‘Ctrl’ and right-click on that station. To switch between the offset positions and original positions for all stations in the network, select ‘Ignore station offsets’ from the ‘Stations’ menu in Snapplot (Figure 3).

Note that moving stations in this manner does not affect the coordinates; it is simply the displayed position that is being changed.

Media enquiries: Brad Young, Land Information New Zealand, phone +64 4 460 0147, email media@linz.govt.nz