Published
One part in ten thousand: the accuracy standard your plat has to meet.
The county has an accuracy standard, and it is a ratio
Most people never read a platting standard, and they do not need to — a surveyor handles it. But there is one number in Fremont County's Appendix L worth knowing even if you never draw a line yourself, because it is the standard your plat either meets or does not.
“Dimensions shall be set in feet and decimal parts thereof, bearings in degrees, minutes and seconds (errors in closure shall not be more than one part in 10,000).”
— Fremont County Development Code, 2011 Edition (Ordinance 2011-04), Appendix L, section 1.02.020. Consolidated through Ordinance 2026-03. Retrieved 1 September 2026
One part in ten thousand. Closure error is the amount by which a surveyed boundary fails to return exactly to its starting point when the measurements are worked around the perimeter. At this standard, a boundary running ten thousand feet may miss by no more than one foot.
That is a real precision requirement, and it is the reason platting is a licensed professional's work rather than a drafting exercise. It is also a useful thing for a landowner to be able to ask about: a surveyor can state the closure achieved on a particular job, and it is a number rather than an opinion.
The drafting requirements, in full
Appendix L applies its general standards to all Sketch, Preliminary and Final Plans and Plats — so the requirements attach at the earliest stage rather than only at the end.
| Requirement | What the appendix specifies |
|---|---|
| Scale | 1 inch = 100 feet, with 1 inch = 200 feet permitted for larger scale projects, unless otherwise approved by the Administrator |
| How scale is shown | In both written and graphic form — the words and a scale bar, not one or the other |
| Dimensions | Feet and decimal parts thereof |
| Bearings | Degrees, minutes and seconds |
| Closure | Errors not more than one part in 10,000 |
| Large areas | May be prepared on multiple, serially numbered sheets with match lines and a sheet index map |
| Where the index goes | The vicinity and index maps appear on the first of the serially numbered sheets, and may be combined |
| Sheet numbering | Each sheet numbered and showing its relationship to the total number of sheets |
| Legend | An adequate legend indicating clearly which features exist and which are proposed |
The requirement to show scale in both written and graphic form is a small thing with a practical reason. A written scale becomes wrong the moment a drawing is photocopied or reduced; a graphic scale bar reduces with the drawing and stays correct. Requiring both means the sheet remains readable however it is reproduced.
The legend requirement does more work than it looks like
Of everything in the general drafting standards, the one most likely to cause an actual problem is deceptively mild: the plan must show an adequate legend indicating clearly which features exist and which are proposed.
That distinction is the single most common source of confusion when a plat is read by somebody who was not present when it was drawn. A road, an easement, a utility line or a building shown without that distinction is ambiguous — and plats are read years later, by lenders, buyers, contractors and officials who have no way to ask.
Requiring the existing-versus-proposed distinction to be explicit in the legend is the county protecting the document's readability over time. It is worth checking on any plat you are handed, because it is the difference between a drawing that answers questions and one that raises them.
What a complete set of general drafting standards asks of a plat, in one list:
- A scale of one inch to 100 feet, or 200 feet on larger projects, or something the Administrator has approved.
- That scale expressed in words and drawn as a bar.
- Dimensions in feet and decimal parts, bearings in degrees, minutes and seconds.
- Closure within one part in 10,000, which the surveyor can state as a figure.
- Serial sheet numbering, match lines and a sheet index map where the plat runs to several sheets.
- Vicinity and index maps on the first sheet, combined if convenient.
- A legend separating existing features from proposed ones, clearly enough that a stranger can tell them apart years later.
Where the standard comes from, and what else applies
The appendix opens by placing itself carefully: it establishes drafting and platting standards for the form and content of subdivision plats, and the requirements it imposes are in addition to the requirements of state law.
That is worth reading precisely. Appendix L is an additional layer, not a complete statement of what a plat must satisfy. Idaho's own platting statutes apply underneath it, and a plat meeting the county's drafting standards has satisfied the county's drafting standards rather than everything that governs it.
The appendix also allows a sensible escape on scale: the specified scales apply unless otherwise approved by the Administrator. Where a parcel's geometry genuinely does not suit 1:100 or 1:200, that is a conversation to have rather than a rule to break.
What a landowner can usefully check
- Ask the surveyor what closure the job achieved, and check it against one part in 10,000. It is a number, not a judgement.
- Confirm the scale is one of the two the appendix names, or that the Administrator has approved something else.
- Check the scale appears both as words and as a scale bar, so the sheet survives copying and reduction.
- On a multi-sheet plat, confirm the vicinity and index maps are on the first sheet and that every sheet shows its relationship to the total.
- Look for match lines on a multi-sheet plat, since they are what make the sheets assemble into a single picture.
- Read the legend specifically for the existing-versus-proposed distinction, because that is what makes the drawing intelligible to someone reading it in ten years.
- Remember these standards are additional to state law, so satisfying them is necessary rather than sufficient.
None of this replaces hiring a competent surveyor, and none of it is a task for a landowner. It is a short list of things you can look for on a document you are being asked to rely on — which is the same reason it is worth knowing who stamps the other drawings in a project, and what their stamp actually certifies — and why two separate code books can govern the same project.
Common questions
What accuracy does Fremont County require on a plat?
Errors in closure shall not be more than one part in 10,000. On a boundary running ten thousand feet, that is a permitted miss of no more than one foot when the measurements are worked around the perimeter.
What scale must a plat be drawn at?
One inch equals 100 feet, with one inch equals 200 feet permitted for larger scale projects, unless otherwise approved by the Administrator. The scale must be shown in both written and graphic form.
Why must the scale appear twice?
A written scale becomes wrong as soon as a drawing is photocopied or reduced, while a graphic scale bar reduces along with the drawing and stays correct. Requiring both keeps the sheet readable however it is reproduced.
How are dimensions and bearings expressed?
Dimensions in feet and decimal parts thereof, and bearings in degrees, minutes and seconds.
Can a plat run to several sheets?
Yes. Plats of large areas may be prepared on multiple, serially numbered sheets with match lines and a sheet index map. The vicinity and index maps appear on the first sheet and may be combined.
What has to appear on each sheet?
Each sheet must be numbered and must show its relationship to the total number of sheets, so a reader can tell whether they are holding a complete set.
What does the legend requirement mean?
The plan must show an adequate legend indicating clearly which features exist and which are proposed. That distinction is what keeps a plat intelligible to somebody reading it years later without being able to ask.
Do these standards apply to preliminary drawings?
Yes. The drafting requirements apply to all Sketch, Preliminary and Final Plans and Plats, so they attach at the earliest stage rather than only to the final document.
Are the county's standards the whole requirement?
No. The appendix states that the requirements it imposes are in addition to the requirements of state law. Meeting the county's drafting standards is necessary rather than sufficient.