Guides
How the work is actually done.
These are the questions the modules were built around, answered on their own terms — useful whether or not you ever open the tool. Where a mistake is common, it is named.
Each guide answers a question the modules here were built around, and answers it on its own terms: the method, the mistakes that are common enough to have cost somebody an afternoon, and how to check your own result before you trust it. You can follow any of them with software you already have — none of them needs this site.
They are written from what these tools actually do, which is why the figures in them are specific rather than round: the fewest control points a transformation can be fitted to, the tax rates an invoice is checked against, the places a name still hides in a PDF whose black rectangles look convincing.
Georeferencing a scanned map: how many control points, and where
Four points in the corners beat twelve along a road. What a control point has to be, how to choose between a polynomial and a spline, and why a near-zero error is often the worst sign of all.
Redacting a PDF so the text is actually gone
A black rectangle is a drawing laid on top; the name underneath survives a copy and paste. What removal actually requires, where else a name hides in a PDF, and how to check a file in two minutes.
Turning a batch of receipts into a CSV your software will import
Reading the figures is the easy half. What to capture per document, why GST and QST belong on their own lines, the rounding that produces false alarms, and why an export badged for your software is usually a trap.