# Artifacts in gamma area maps images?

**URL:** <https://forum.orfeo-toolbox.org/t/artifacts-in-gamma-area-maps-images/3447>\
**Category:** S1 Tiling\
**Created:** [September 21, 2026, 8:08am UTC](https://forum.orfeo-toolbox.org/t/artifacts-in-gamma-area-maps-images/3447 "2026-09-21T08:08:22Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![remi.cresson](https://forum.orfeo-toolbox.org/user_avatar/forum.orfeo-toolbox.org/remi.cresson/32/1270_2.png) [@remi.cresson](https://forum.orfeo-toolbox.org/u/remi.cresson)\
**Post date:** [September 21, 2026, 8:08am UTC](https://forum.orfeo-toolbox.org/t/artifacts-in-gamma-area-maps-images/3447/1 "2026-09-21T08:08:22Z")

</div>

Hi,

I am playing with S1Tiling to generate gamma-rtc calibrated images. I noticed some kind of “lines” artifacts in the output images, particularly in mountain area. These artifacts seem to come the gamma area map itself.

Below is a screen capture (area is located on MGRS tile 31TDH, orbit #132). Most values are roughly in the [25, 500] range, and white pixels where the lines are, carry very high values (say \> 1000).

 ![image](https://forum.orfeo-toolbox.org/uploads/default/original/2X/8/83d0f8e350fe7b91fcd842e4e92eefe138de193c.jpeg)

I used a 30m resolution SRTM DEM, with there settings:

```ini
[Processing]
cache_dem_by: copy
calibration: gamma_naught_rtc
remove_thermal_noise: True
lower_signal_value : 1e-7
use_resampled_dem: True
resample_dem_factor_x: 2.0
resample_dem_factor_y: 2.0
distribute_area: False
min_gamma_area: 1.0
calibration_factor: 1.0
output_nodata: False
output_spatial_resolution : 10.
orthorectification_gridspacing : 40
orthorectification_interpolation_method : bco
mode : Normal
# Required for gamma maps
ram_per_process : 70000
disable_streaming.gamma_area : True
creation_options.s1_on_dem : float64 COMPRESS=DEFLATE, BIGTIFF=YES, PREDICTOR=3, TILED=YES, BLOCKXSIZE=1024, BLOCKYSIZE=1024

```

In [Small et al](https://ai4edatasetspublicassets.blob.core.windows.net/assets/pdfs/sentinel-1/2011_Flattening_Gamma.pdf). it is stated that a low res DHM (less than the image resolution) would cause some content loss. Do you think that the `resample_dem_factor_x/y` is the culprit here? Should/could I configure my process differently to avoid these obviously not expected artifacts?

Many thanks for this magnificent piece of software, and for your help!