Putting true shapes into Archie-M is fraught with a number of difficulties, not least of which is getting the survey right.

**Some basic rules**:

If the survey accuracy (not the precision!) is not better than about 20mm don't bother, fit a standard shape. If you survey using a total station, you will pass this barrier, but not if you use a tape and staff.

You need a group of survey points near each end and near any definite changes in slope. The ends are particularly important if the shape is not approximately circular. The absolute minimum is 9 points round the arch. If they are spaced roughly equally round the curve (note not equal spaces horizontally), adding one between the end two at each end will dramatically improve the fit.

**Getting the data in**:

It is best to do a simple check before you input the data. put the numbers (x and y coordinates) into Excel as two columns and plot the result as an xyplot using the curve fit option. If the curve doesn't look good in excel it will not look good in Archie-M. You can often overcome this difficulty by adding extra points by eye. Adding points is much easier in Excel because you can simply insert a row. adding a row in Archie-M adds it at the bottom and you then have to move the numbers down one at a time.

Once you have two columns of numbers which plot effectively, save them as a .prn file. This option is available in the save as list for excel.

The final step is to rename the file as .sur

Once it is in that form it can be read into Archie-M.

Note that the data points should start in A1, there should be no labels and no numbering of the points, just two columns of numbers.

We are working on a new version of Archie-M and hope to improve some aspects of the data input.

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