> For the complete documentation index, see [llms.txt](https://docs.innova-drilling.com/introduction/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.innova-drilling.com/introduction/legacy-documentation/manuals/well-seeker-pro-1/appendix-d-error-model-description.md).

# Appendix D – Error Model Description

The error model implemented in Well Seeker is the ISCWSA MWD error model as described in SPE paper 67616 by H. Williamson. This paper contains a full explanation of the ISCWSA work. The error model used within this program uses the error terms and one sigma magnitudes described below.

![](https://100379801-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-McEwHTOM_v4MexTVGSe%2F-MhYbXHJdfBjMNPqTcYC%2F-MhYbtBn3Ny2iF8EAI8N%2F16.PNG?alt=media\&token=827331a1-9c53-4131-9bfb-9fa887f9b66b)

The model does not use any bias terms and it implements the latest misalignment and tool face independent terms as listed below.

![](https://100379801-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2Finnova-engineering-how-to-guides%2F-MhYbXHJdfBjMNPqTcYC%2F-MhYbg7p6j_UTxAvDuvu%2F1.png?generation=1629463954596078\&alt=media)

![](https://100379801-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-McEwHTOM_v4MexTVGSe%2F-MhYc0lNVDUH-sFRmZG6%2F-MhYc9UkPdU8XwIoRCju%2F17.PNG?alt=media\&token=1abb9589-53e3-4197-83a4-b2f3e6523852)

![](https://100379801-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-McEwHTOM_v4MexTVGSe%2F-MhYc0lNVDUH-sFRmZG6%2F-MhYcND_v46sGMhMW6M9%2F18.PNG?alt=media\&token=4025f15c-1d01-46e3-8d0f-f2cdcb4c13db)

Misalignment terms taken from SPE90408 by Torkildsen, Ekseth, Weston, Havardstein and TF independent terms from “Borehole survey error model documentation” – CDR-SM-03 – by Copsegrove Developments.


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