I need higher accuracy than 1-2%. Can I submit my own dimensions to improve accuracy?

The Short Answer

On its own, using Canvas with a LiDAR-enabled device will yield accuracy tolerances of within 1-2% of manually verified dimensions. This is largely a function of the devices themselves, and you can read more about expected tolerances here: What kind of accuracy can I expect from Canvas?

If you require a higher degree of accuracy for specific critical dimensions, you may always send in manually-verified field measurements to accompany a Scan To CAD order. This will "override" the scan for the measurements provided (where possible), and use the scan data for the rest. 

To submit reference dimensions, please email our support team at support@canvas.io with your documents and referencing your order ID.

The Long Answer

Reference Material Accuracy

Please note that when measurements are provided for incorporation into your Scan To CAD order, we rely fully on both the accuracy of your measurements and the readability of your reference material. If the measurements provided are themselves inaccurate, or unclear what they refer to, this can lead to inaccuracies in your Scan To CAD order or additional questions and revisions which delay your order. While we always will make our best effort to bridge the gap with you, we can not guarantee that all dimensions will precisely match. 

In the rare case that reference material varies significantly from the scan, we will be unable to override the data from the scan without risking introducing significantly larger errors. This threshold is 6" for measurements under 300", and 12" for measurements above 300".  


Provided dimensions are not used to "scale" the rest of the model, and are instead solely used to override that particular measurement from the scan. Error in 3D scanning is not uniform, so scaling all dimensions according to a single or few reference dimensions will not always make other dimensions more accurate. However, providing reference dimensions does have the effect of controlling error during the process and producing a more accurate overall model. 

Guidelines For Submitting Manual Measurements

When submitting a drawing with manual measurements, please follow these guidelines:

  • Your verified dimensions must be annotated in clear and legible text or handwriting, using English characters. 
  • Imperial or metric units are both acceptable.
  • The start and endpoint for any dimension must be clear and unambiguous from the drawing, and not rely on "industry-standard" assumptions (e.g., does a door opening dimension include the casing around it or not - these vary significantly across industries).
  • Send your drawing as an image or PDF — if you send a .dwg file it may require additional time to triage.
  • A digital drawing is preferred, but a photo of a hand drawing is also acceptable if the photo is clear and readable. 
  • Include the order ID in the subject line and send to support@canvas.io as soon as possible after you upload your scans.

Here is an example of a totally acceptable drawing submitted by a customer with their order as extra reference: