Two suggested additions to the manual's "Scale raster" tool section:
1) Given the map scale, e.g., 1:10000, that value can be entered as (10000,DPI) ONLY IF the CRS is using meters.
However, if the CRS is using ftUS, then the scale must be 3.280084 X map scale, i.e., (32800.84, DPI)
In other words, the scale value must be CRS Units / Meter
2) for manually scaling a survey plan when the plan scale is not known or the DPI is uncertain I have found the following to be useful:
load the image using FreehandRasterGeoreferencer (FRG)
Meas = line on survey measured using QGIS Measure tool
Indic = length of same line as indicated on the survey
FRG_scale = scale indicated in layer info (by double clicking on layer)
calculate B = (Meas/Indic) * 2540 / FRG_scale
ctrl-click in image with Scale tool and enter (100000,B)
That will adjust the image to match the Survey length with the as scaled length. It can then be Moved or Rotated to align with the map.
FRG is a wonderful plug-in. I have found it essential for georeferencing surveys. Many thanks!
Two suggested additions to the manual's "Scale raster" tool section:
1) Given the map scale, e.g., 1:10000, that value can be entered as (10000,DPI) ONLY IF the CRS is using meters. However, if the CRS is using ftUS, then the scale must be 3.280084 X map scale, i.e., (32800.84, DPI) In other words, the scale value must be CRS Units / Meter
2) for manually scaling a survey plan when the plan scale is not known or the DPI is uncertain I have found the following to be useful: load the image using FreehandRasterGeoreferencer (FRG) Meas = line on survey measured using QGIS Measure tool Indic = length of same line as indicated on the survey FRG_scale = scale indicated in layer info (by double clicking on layer) calculate B = (Meas/Indic) * 2540 / FRG_scale ctrl-click in image with Scale tool and enter (100000,B) That will adjust the image to match the Survey length with the as scaled length. It can then be Moved or Rotated to align with the map.
FRG is a wonderful plug-in. I have found it essential for georeferencing surveys. Many thanks!