From a drawing to a recording sheet
A lux level survey is a grid of readings, and the slow part has never been taking them. It is
ruling a metre grid over a drawing by hand, numbering every square in red pen, walking the site
with that sheet, and then retyping a few hundred numbers into a spreadsheet and rebuilding the
statistics from scratch. On a nine-metre island platform ninety metres long that is over eight
hundred squares drawn and numbered twice, once on paper and once in Excel, before anybody has
looked at a single result.
This tool collapses that to a few minutes. Set the scale, outline the area, mark what the survey
should skip, and it produces both halves of the pack at once: the workbook whose cells are the
grid, and the drawing whose squares carry the same references. Because they come out of the same
calculation they cannot drift apart, which is the failure that makes a completed survey
worthless — readings that all landed, and all landed in the wrong square.
Setting the scale, and the trap in the title block
Most drawings that reach a surveyor are scans: a large plot, photocopied or run through a
scanner, arriving as a raster image inside a PDF with no vector geometry and no text layer. The
scale printed in the title block belongs to the sheet the drawing was plotted on, not
the file you were sent. Reduce an A1 plot to A3 and you have halved it — two paper steps, a
factor of two exactly — so that 1:100 is now 1:200, and a grid built on the printed figure comes
out at half size with nothing to reveal the error until somebody paces the platform.
The reliable route is to measure. Pick two points on the drawing whose real separation you know
and type it in; the scale then comes from the drawing itself and the title block never enters
into it. The tool still reads the PDF page size and tells you which ISO sheet it looks like, and
if you have both measured something and typed a scale it tells you how far apart the two answers
are, because a factor of two is not a rounding error.
What comes out
The workbook is one worksheet per area, with the grid repeated side by side for each lighting
scenario — normal, emergency at zero hours, emergency at three hours, or whatever set you name.
Row numbers run down the long axis and column letters across the short one, so a long platform
is a tall sheet rather than an unusable ninety-column one. Obstructions are merged, shaded,
labelled and locked. Cells outside the outline are shaded and locked too, so a reading cannot be
typed into a square that is not part of the survey, and with the sheet protected the Tab key
walks only the squares that are.
Under each grid sit the statistics as live formulas: average, maximum, minimum,
a count of readings entered, min/max diversity and uniformity as Emin ÷ Eaverage, each over its
own zone, followed by the targets you entered, the source you took them from, and a Pass/Fail
that stays blank until there is both a target and a reading. A final sheet records what every
zone was judged against, together with the VERIFY register — what the tool holds, and what it
does not.
Alongside it comes the marked-up drawing, as a PNG or through the printable pack. By default the
references are labelled along the edges rather than written into every square, because eight
hundred labels on a platform drawing is unreadable at any size a person can carry and the axes
carry exactly the same information — you read off a letter and a number the way you would on a
chessboard. For a small plant room, per-cell labels are a click away.
Where this sits
This is a survey tool: it records what a space measures now. Designing what it ought to measure
is a different job, and the lighting design
calculator on this site does the first pass of it by the lumen method. When a survey shows a
space failing and the question becomes what to install, that is a
DIALux lighting design — point-by-point illuminance,
uniformity, glare and a submission-ready pack. A survey grid tells you where you are; it does
not tell you what to fit.
How do I set the scale on a scanned drawing?
Measure it. Click the two ends of something on the drawing whose real length you know — a platform, a bay, a dimensioned wall — and type that length in metres. The tool works out metres per pixel from those two clicks. You can type a scale instead, but only when the PDF page really is the sheet the drawing was plotted on, and very often it is not: a drawing plotted at A1 and scanned to A3 has lost a factor of two, so its title-block 1:100 is 1:200 on the file and every cell would come out half size. The tool tells you what sheet size it thinks the page is, and if you have also measured something it tells you how far the two disagree.
What size should the measurement grid be?
One metre is the usual grid for a station platform or a concourse survey and it is what the tool defaults to, but it is a default and not a rule. BS EN 12464-1 sets out how a measurement grid should be spaced, and the spacing it gives depends on the size of the area, so a large hall and a small plant room do not get the same grid. This tool does not reproduce that rule and does not claim your cell size is standard-mandated — set the cell size to whatever the governing standard or the project specification calls for, and record which one you used.
How does it handle a lift shaft, a switchroom or a bank of seats?
Draw round it as an obstruction and give it a name. Those cells stay on the drawing so the surveyor can see what is there, but they are written into the workbook as a merged, shaded, labelled block instead of an empty square, they are locked so nobody can type a reading into them, and they are skipped by the average, the minimum and the maximum. Whether an obstructed area ought to be excluded from the assessment at all is a judgement about the space rather than something an outline can decide for you.
Does the spreadsheet work out the uniformity and the Pass/Fail itself?
Yes — the workbook ships with live Excel formulas, not pasted numbers. Type your readings into the squares on site and the sheet computes the average, the maximum, the minimum, the min/max diversity and the uniformity (Emin ÷ Eaverage) for each zone, then compares them with the targets you entered and returns Pass or Fail. It stays blank until there is something to judge, so an unfilled sheet reads as empty rather than as a failure. There is also a colour scale over the reading area, so the sheet heat-maps itself as you fill it in.
Why does the tool not offer uniformity targets?
Because it does not hold them, and a target on an issued survey sheet needs a source. The illuminance targets you can pick from a list are an indicative subset of BS EN 12464-1 that you should still verify against the standard for your exact task; there is no equivalent list of uniformity figures in the tool, and filling one in with a plausible number would put an unsourced value on a document somebody signs. Enter the uniformity target yourself along with where it came from — the standard, the client specification, a transport authority standard — and the tool prints it on the sheet exactly as you typed it.
Can I do a whole station in one file?
Yes. A project holds as many areas as you like, each with its own drawing, its own scale, its own grid and its own acceptance criteria, and the export gives you one workbook with a worksheet per area plus a criteria sheet recording what each was judged against. That is the shape a real survey takes — a platform, a footbridge and a ticket hall are three different drawings at three different scales. The whole project saves to a JSON file you can reopen later, optionally with the drawings embedded so it opens on its own.
What if the room is at an angle on the drawing, or is not rectangular?
Use the grid axis tool and click two points along a wall — the lattice then runs parallel to that wall instead of to the page, which matters because a platform drawn three degrees off square produces a grid that lines up with nothing and a surveyor who cannot tell which square they are standing in. The outline itself is a free polygon, so L-shaped footbridges, splayed concourses and rooms with a corner taken out all grid correctly; cells outside the outline are shaded and locked in the workbook.
Is my drawing uploaded to a server?
No. The whole tool runs in your browser — the PDF is rendered locally, the grid is worked out locally, and the workbook and the marked-up drawing are generated locally and handed straight to your downloads. Nothing you open here is transmitted anywhere, which matters when the drawing is a client deliverable or covers a station. The page sets no tracking cookies either, which is why there is no cookie banner on it.