1

I have QGIS 3.10.7 and QGIS 2.12.3. I am loading the same ASCII (.asc) file into both versions of QGIS. QGIS 3.10.7 says the values in the ASCII file range from 186.573 - 1458.33. QGIS 2.12.3 says the values range from 267.966 - 1142.93.

ArcMap says the range is 549.979 - 1462.79.

Do different programs interpret ASCII files differently? If I were to use SAGA tools to calculate something like slope/aspect/topographic position index using the different programs, I assume the results would be different in absolute terms, but would they be the same/similar in relative terms?

10
  • 1
    Have you made sure you use the same CRS in all GIS?
    – Erik
    Commented Jun 26, 2020 at 14:32
  • 1
    How are you checkinc the values?
    – Bera
    Commented Jun 26, 2020 at 15:26
  • 2
    Are you sure that the range you get are from the whole value and not from a subset, check the option on all 3 software
    – J.R
    Commented Jun 26, 2020 at 15:33
  • 1
    Link to test data would leave less space for quessing. Also describe how did you exactly get the values so it would be possible to do the same.
    – user30184
    Commented Jun 26, 2020 at 15:40
  • 1
    Does ArcMap show the min/max of data? Or does if report the highest and lowest value used for stretching the color ramp?
    – user30184
    Commented Jun 26, 2020 at 15:43

1 Answer 1

5

QGIS is just estimating the statistics from a sample, instead of calculating the actual statistics from all of the values.

In the QGIS layer properties - Symbology - Min / Max Value Settings change the Accuracy setting from Estimate (faster) to Actual (slower).

enter image description here

2
  • while the accuracy is set to "estimate'', will it produce different results than the accuracy set to -'Actual', for any raster processing such as zonal statistics?
    – GIStree
    Commented Mar 22 at 5:25
  • 1
    The statistics this q refers to are only used for display. They don't affect processing.
    – user2856
    Commented Mar 23 at 2:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.