Figures and drawings that make a technical chapter readable

The figures in a technical report get read before the text, and on many applications they are the only part of the chapter a case officer studies closely. Technical report figures and drawings therefore have to work twice: on a laptop screen at 100 per cent, and on a black and white A4 print made by someone in a hurry. A constraints plan that relies on four shades of green fails the second test completely, and with it the argument the chapter was making.

None of this is about making documents pretty. It is about whether the reader can find the site, see what constrains it, and follow the reference from the paragraph to the plan without opening a second file.

Why figures do the persuading

An officer writing a report has a fortnight, twelve applications and a committee date. They will read your conclusions, scan the method, and look hard at the plans, because the plans are where they check whether you understood the site.

Three things follow. A figure has to be legible without the text around it, which means a title that states what it shows rather than "Figure 4.2". It has to be self-contained, with a legend covering every symbol on it. And it has to be findable, which means the text says "Figure 4.2" at the point the reader needs it rather than gesturing at "the plans below".

The same applies to consultees, who often read only the figure relevant to their topic. A highway officer opens the access plan. An ecologist opens the habitat plan. Neither will hunt through a 90 page appendix.

Constraints plans and layering conventions

The commonest failure is one plan carrying fourteen designations. Split them by theme, and accept more plans rather than more layers.

A workable order, bottom to top: base mapping in pale grey, area designations as hatches or tints, linear features such as watercourses and public rights of way, point features such as listed buildings and trees, then the application site boundary on top in red so nothing obscures it.

Use hatch patterns as well as tints for area designations, because two tints of similar value become identical in monochrome while diagonal hatching against cross hatching survives. Keep tint transparency consistent, and never stack three tints over one another: where designations overlap, say so in a note or produce a separate plan.

Make the red line identical to the application red line, drawing for drawing. An officer who spots a constraints plan boundary that differs from the location plan will query every other figure in the document.

Cite the source of each layer in the figure notes, with the date it was downloaded. National datasets, the multi-agency mapping service and the heritage list are the usual sources, and naming them removes an easy challenge.

Legends, scales and north points

Every plan needs four things and they are absent from perhaps a third of figures submitted.

• A legend showing every symbol present, and nothing that is not
• A north point, on every plan, oriented correctly
• A scale bar plus a written scale with the sheet size stated, such as 1:1250 at A3
• The figure title, number and the report it belongs to

State the sheet size with the scale, because a plan printed at 1:1250 at A3 becomes 1:1768 at A4 and a measurement taken off it will be wrong. Where a figure is not to scale, mark it not to scale rather than leaving a bar that no longer matches.

Mind the licensing of base mapping. Mapping supplied under licence carries conditions about reproduction and attribution, and the licence number belongs in the figure notes. Open data alternatives exist for constraints work and are worth using where the accuracy suits the purpose.

Minimum text size matters more than designers expect. Aim for legibility at the final print size rather than on screen, and check by printing one page rather than by zooming out.

Numbering and referencing discipline

Number figures by chapter, so Figure 8.3 is the third figure of chapter 8. Keep a figure list at the front of the volume with titles and page or file references.

Then three rules. Every figure is referenced at least once in the text, or it comes out. No figure is renumbered after issue, because consultees quote numbers in their responses, so a change adds 8.3a rather than shifting everything below it. And figures referred to in more than one chapter live in one place, with the other chapter cross-referring to the original number.

Where photographs are used, they need a viewpoint plan with numbered camera positions and arrows, plus the date and the focal length for each shot. Visual material prepared for landscape work follows its own conventions, set out in the note on photomontage methodology for landscape and visual assessment, and daylight material follows the conventions described for shadow plots and their dates.

Colour choices that survive a monochrome print

Assume every figure will be printed in black and white at some point, because in many authorities it will be.

Test it. Print one copy of each plan in greyscale and look at whether the categories remain distinguishable. Where they do not, differentiate by pattern, line weight or label rather than by hue alone.

Avoid red and green as the only distinction between two categories, since that pairing is the hardest for a substantial proportion of readers to separate, and it also converts to nearly identical greys. Use a light to dark progression for ordered categories such as flood zones or risk bands, and reserve saturated colour for the one thing you want noticed.

Line weights carry more information than colour in practice. A 0.7 millimetre site boundary, a 0.35 millimetre designation edge and a 0.18 millimetre base map line read correctly at any print size, and they survive photocopying.

Tables against figures

Choose by what the reader has to do with the information.

Never submit a table as a flattened image. It cannot be searched, it cannot be copied into an officer report, and it prints badly. The same discipline applies to a schedule such as the condition grading in a structural survey defect schedule, which is a table doing a table's job and should stay one.

Keep numbers in tables consistent with the text. A residual effect described as moderate adverse in the paragraph and minor adverse in the table is the single most damaging error in a technical chapter, because it invites the reader to distrust everything else.

A pre-issue check on every figure

• Title states what the figure shows, not just its number
• Figure number matches the reference in the text
• Legend covers every symbol, and nothing absent from the plan
• North point present and correct
• Scale bar with written scale and sheet size, or marked not to scale
• Site boundary identical to the application red line
• Data sources and download dates in the notes
• Base mapping licence acknowledged
• Greyscale print checked for category separation
• Smallest text legible at final print size
• File exported as vector where possible, and within the portal's file size limit
• File name matches the figure number and title

That list takes ten minutes per figure and removes almost every query a validation officer raises about drawings.

Illustrative example: a chapter originally carried one constraints plan with flood zones, conservation area, listed buildings, a Tree Preservation Order and two habitat designations in overlapping tints. Split into three plans, one for heritage, one for ecology and trees, one for flood and drainage, each with its own legend and a consistent red line, it went through validation without a query and the consultee responses referred to the plans by number. Details are illustrative.

PlanScope drafts the written structure of technical reports and flags the site facts it does not have rather than inventing them, leaving the figures to be prepared by whoever holds the survey data. Browse all 66 PlanScope report types to see which documents a scheme needs and what each one has to show.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.