# Error element face midpoint distance **URL:** \ **Category:** SPECFEM\ **Created:** [September 18, 2020, 3:49pm UTC](https://community.geodynamics.org/t/error-element-face-midpoint-distance/1456 "2020-09-18T15:49:15Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![jflorescuba](https://avatars.discourse-cdn.com/v4/letter/j/ecae2f/32.png) [@jflorescuba](https://community.geodynamics.org/u/jflorescuba)\ **Post date:** [September 18, 2020, 3:49pm UTC](https://community.geodynamics.org/t/error-element-face-midpoint-distance/1456/1 "2020-09-18T15:49:15Z")
Hello I am trying to run specfem3D for a mesh (2layer model) of 5kmx5kmx5km and element size 120m. I am using the stacey absorbing condition. when the database generation is running, I got the following message. running database generation… error element face midpoint distance: 0.250000000 - edge length: 899.995422 tolerance: 8.99995416E-02 error corner: 1 xyz: 1040620.06 6291391.00 -191.233078 error corner: 2 xyz: 1040620.06 6291391.00 -161.232971 error corner: 3 xyz: 1040721.06 6291418.50 -159.854706 error corner: 4 xyz: 1040721.06 6291418.50 -189.854630 reference : 1 xyz: 1040721.06 6291418.50 -189.854630 reference : 2 xyz: 1040721.06 6291418.50 -159.854706 reference : 3 xyz: 1040620.06 6291391.00 -161.232971 reference : 4 xyz: 1040620.06 6291391.00 -191.233078 error element face midpoint distance: 0.250000000 - edge length: 900.000000 tolerance: 8.99999961E-02 error corner: 1 xyz: 1037963.50 6292375.00 -164.766586 error corner: 2 xyz: 1037963.50 6292490.00 -166.629639 error corner: 3 xyz: 1037963.50 6292486.50 -106.794266 error corner: 4 xyz: 1037963.50 6292375.00 -134.766586 reference : 1 xyz: 1037963.50 6292375.00 -164.766586 reference : 2 xyz: 1037963.50 6292375.00 -134.766586 reference : 3 xyz: 1037963.50 6292486.50 -106.794266 reference : 4 xyz: 1037963.50 6292490.00 -166.629639 error element face midpoint distance: 0.253906250 - edge length: 900.045349 tolerance: 9.00045335E-02 error corner: 1 xyz: 1041508.19 6294986.50 -98.7428589 error corner: 2 xyz: 1041508.25 6294986.50 -68.7457809 error corner: 3 xyz: 1041431.06 6295078.00 -58.3097878 error corner: 4 xyz: 1041431.12 6295078.00 -88.3104782 reference : 1 xyz: 1041431.12 6295078.00 -88.3104782 reference : 2 xyz: 1041431.06 6295078.00 -58.3097878 reference : 3 xyz: 1041508.25 6294986.50 -68.7457809 reference : 4 xyz: 1041508.19 6294986.50 -98.7428589 error element face midpoint distance: 0.250000000 - edge length: 1841.46899 tolerance: 0.184146896 error corner: 1 xyz: 1037963.50 6294120.00 -22.6280594 error corner: 2 xyz: 1037963.50 6294119.00 19.5043087 error corner: 3 xyz: 1037963.50 6293996.50 19.3953953 error corner: 4 xyz: 1037963.50 6293997.50 -23.5052948 reference : 1 xyz: 1037963.50 6293997.50 -23.5052948 reference : 2 xyz: 1037963.50 6293996.50 19.3953953 reference : 3 xyz: 1037963.50 6294119.00 19.5043087 reference : 4 xyz: 1037963.50 6294120.00 -22.6280594 STOP error element face midpoint STOP error element face midpoint STOP error element face midpoint STOP error element face midpoint any suggestions? Thanks ---
**Author:** ![dpeter](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/dpeter/32/227_2.png) [@dpeter](https://community.geodynamics.org/u/dpeter)\ **Post date:** [September 21, 2020, 9:59am UTC](https://community.geodynamics.org/t/error-element-face-midpoint-distance/1456/2 "2020-09-21T09:59:07Z")
looks like your mesh coordinates are a bit large (e.g. y-coordinates around 6,294,120 m) which makes the numerical precision less sensitive, thus the default tolerance value for these face detections becomes too small. as a quick check to see if things would go round, you could modify the tolerance value in file src/shared/get\_element\_face.f90 (around line 57): … ! distance tolerance (relative to coordinate range) real(kind=CUSTOM\_REAL), parameter :: TOL\_DIST = 1.e-4 … to something like: real(kind=CUSTOM\_REAL), parameter :: TOL\_DIST = 1.e-3 which would be enough for the values given in your output log.