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Hi Robert, I'll start a discussion; others who do similar calculations might be able to add more detail. You can get data along any curve, such as a diagonal, with the SAMPLEXY function. In the Users Guide under "SAMPLEXY, function definition", there is an example which defines a straight line and samples a field along it. The result of sampling an X-Y-Z field along a curve is an X-by- Z result, where X is now an index, the count of points along the curve or diagonal line. There is a discussion of what Ferret does with 2-dimensional integrals on latitude-longitude grids, in Chapter 3, the section called "General information about transformations." It doesn't sound like you are doing a 2-dimensional integral, but, "If @DIN is applied simultaneously to both the X and Y axes (in units of degrees of longitude and latitude, respectively) the calculation will be carried out on a per-unit-area basis (as a true double integral) instead of a per-unit-length basis, sequentially." Also, when the axis units are longitude and latitude, Ferret applies a latitude correction for integrals and averages. This may be why you are seeing unexpected results for your integrations.. The reference for this discussion in the Users Guide is under "COSINE(latituude)" in the index. Here is a relevant paragraph: "When calculating integrals and derivatives (@IIN, @DIN, @DDC, @DDF, and @DDB) Ferret attempts to use standardized units for the grid coordinates. If the underlying axis is in a known unit of length Ferret converts grid box lengths to meters. If the underlying axis is in a known unit of time Ferret converts grid box lengths to seconds. If the underlying axis is degrees of longitude a factor of COSINE (latitude) is applied to the grid box lengths in meters. " Ansley Manke Robert Landsberger wrote: Dear Ferreters, |