> 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/innova-engineering-manual/well-seeker-x-manual/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.
The model does not use any bias terms and it implements the latest misalignment and tool face independent terms as listed below.
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