Hydrographic survey PDF to CSV, without tracing in CAD
A hydrographic or bathymetric survey often reaches you only as a plotted sheet: the depth soundings are there, printed as spot soundings beside their marks, but the hydrographic data behind them isn't. When you need the numbers as data, for a comparison survey, a surface or a quantity check, the sheet is all you have.
If the PDF came out of CAD or GIS, the depths in it are usually still real numbers, not pixels. That's what makes reading them out automatically possible.
What ensoundings does
ensoundings reads the depths straight out of the PDF and gives them back as a CSV, one row per sounding:
Example rows, in the real format.
- Easting and northing
- Georeferenced from the coordinate grid printed on the sheet itself, such as border labels like E 875,000 or X=486000. The values stay in that grid's own system and units, whether that's state plane, UTM or a local grid, exactly as labelled. Nothing is converted or reprojected.
- Depth
- The number as printed, in the sheet's own units and relative to its own datum, such as MLLW, MLW, NAVD88 or chart datum. No rounding, no sign change, no conversion.
- Confidence
- How clear the reading was, from 0 to 1. Points that need a second look are flagged for you to check.
If a sheet has no coordinate grid the reader can use, the file says so. It then gives positions on the page instead of real-world coordinates, and never presents those as eastings and northings.
The CSV opens directly in Excel, so this is a PDF-to-Excel step as well, and it imports as points into AutoCAD, Civil 3D, ArcGIS, QGIS or HYPACK.
Why tracing takes so long
The manual route is familiar: insert the PDF into CAD, scale and position it on the grid, then place a point on every sounding and type its depth. A busy sheet holds thousands of soundings, so that's a day or more of careful clicking, followed by a second pass to catch the typos and the soundings you skipped.
Reading the depths from the PDF removes the typing and the positioning, and leaves the part that needs a person: checking the result.
Will it work on your sheet?
Honestly, it depends on how the PDF was made. The quickest way to find out is to try it: you see every sounding it found, laid over your sheet, before you pay anything. A sheet it can't read costs nothing.
Most likely to work
- One-page vector PDFs exported from CAD or GIS. These are the “original” PDFs, not scans.
- Depths printed as decimal numbers next to their marks, such as 17.1 or 9.8, whether typed as text or drawn as line work.
- A coordinate grid labelled around the border.
- One sheet at a time. From a plan set with several sheets, you pick the sheet to convert, and you can outline just the soundings on it.
Not supported yet
- Scanned or photographed sheets, or any PDF that is just an image of a drawing.
- Depths shown only as contour lines (isobaths) or shaded bands. On the roadmap.
- Depths written as whole numbers with no decimal. On the roadmap.
- Very large or very dense drawings. If one can't be processed, you're told why and charged nothing.
How it works
- Upload a vector PDF and pick the sheet to convert from the window that opens. To read only part of it, click around the soundings to outline them; otherwise the whole sheet is read.
- Review the result: the number of soundings, the overall confidence, and every flagged point. No account is needed.
- Pay and download once you're happy: $75 per sheet, or less with a monthly plan. You get the CSV immediately and can download it again any time within 18 months.
Your PDF is used to make the conversion and isn't kept afterwards.
Common questions
Does it work on scanned surveys?
No. A scan is a picture of the sheet, with no numbers inside it to read. ensoundings reads vector PDFs, the kind exported from CAD or GIS.
Is the output georeferenced, and in which coordinate system?
Yes, from the grid printed around the sheet's border, and the values stay in that grid's system and units: state plane, UTM or a local grid, as labelled. Nothing is reprojected, so check the sheet's notes for the projection.
Are the depths in feet or meters, and to which datum?
Whatever the sheet uses. Depths are written exactly as printed, so they stay in the sheet's units and relative to its datum, such as MLLW, MLW, NAVD88 or chart datum. Check the sheet's notes.
Does it read multibeam, single-beam or sonar data?
No. ensoundings reads soundings already plotted on a PDF. Raw multibeam, single-beam echo sounder, sonar or lidar data needs survey processing software; ensoundings is for the sheet that came out at the end.
What if it misreads a sounding?
Every point carries a confidence score, and the ones that need a second look are flagged in the review before you pay. Check them against the sheet.
Before you rely on it
The CSV is a reading of a drawing, not a new survey. It can only be as accurate as the sheet it came from, and an automatic reader can miss or misread a sounding. That's why every point carries a confidence score and why the review step exists. For estimating and checking, verify against the source sheet. Before using the data for anything where depth is a safety matter, or as the basis of a bid or design, have a licensed surveyor check it.
Try it on your sheet
Upload a sheet and see what it reads before you pay anything.