Test Form - 11_Ab02PV

Steffi LaZerte

2021-07-21

Source: vignettes/reports/11_Ab02PV_compare_report_form.Rmd

Details

  • 0.27 min to run
  • /home/steffi/Projects/Business/LandmapR/Runs - FlowMapR/Steffi_LandMapR_tests/11_Ab02PV/FlowMapR original FormMapR output
  • grid = 5
  • str_val = 200
  • ridge_val = 200

Missing values

In the original FormMapR, cells with missing elevations were generally given values of zero or 1. However, in LITAP, they remain as NA (missing) to more accurately reflect the nature of the measurement.

By cell or by grid

LITAP’s form_mapper() outputs two versions of qweti, lnqarea, and qarea. The first ones (compared here), are qweti1, lnqarea1 and qarea1 in the file dem_weti. Area in these values is based on the number of cells. In the other measures (not compared here; qweti2, lnqarea2 and qarea2), area is based on actual grid cell area.

qweti1, lnqarea1 and qarea1 are values are compatible with facet_mapper()

Rounding error

Many calculated values differ by minute amounts due to differences in rounding over long calculations.

  • prof and plan are particularly sensitive as they use trigonometry calculations which result in many small discrepancies.
  • qarea and qweti also experience a build of up differences, as they add cell-by-cell and small differences mount up in cells which contain input from many others

However in all cases the are small differences, often resulting in < 1% changes.

Visual Comparison of Form

Original vs. New Form values

Original vs. New Relief values

Original vs. New Length values

NOTE

Length to divide (l2div) is the distance from the focal cell to the nearest crest cell.

In the original Fox Pro version, this is calculated by first getting the ‘flat distance’ (focal row/col to crest row/col), and then accounting for elevation by using z2cr (the elevation difference between focal and crest cells).

However, in the C++ version z2cr was changed to the z2peak, which is the elevation difference between the focal cell and the nearest peak cell. I believe is incorrect; therefore LITAP uses the original calculation with distance to nearest crest cell (z2cr).

This results in discrepancies between LITAP and FormMapR for l2div, lstr2div, and pstr2divl.