Work With QTO Sessions

Choose the Right Workspace

Start in Quantos when you do not yet have a project. Save a private draft to keep the work, then link that same session to a project before generating an estimate.

Choose Standalone or Project-Backed QTO

If you need to…	Use…	What Darwin keeps
Inspect a file without saving it	Local viewer / scratch work	Drawing scratch measurements are journaled locally per file; an unsaved IFC analysis is recomputed from the file
Keep work before choosing a project	A saved Quantos draft	A private session visible only to its creator
Generate or apply estimate quantities	A linked project QTO session	The same session, with its project, mappings, and accepted quantity evidence

The older standalone PDF viewer remains a local inspection/export tool. Use Quantos’s explicit draft save when you need durable work that can later join a project.

Save and Link a Quantos Draft

1. Open a drawing or model in Quantos and inspect it.
2. Explicitly save it as a draft. Before that save, the work is not stored in Darwin’s project records.
3. Reopen the private draft when you are ready to continue.
4. Link it to a project. Darwin files the drawing in 2D Plans or the model in IFC Models, without making you re-upload it or recreate the session.

Saved drafts appear under My drafts on the Quantos viewers. A draft is private: its header reads Draft · only you, and only its creator can list, open, edit, or delete it. Opening a draft that has already been linked redirects you to the project it belongs to. When you link, Darwin warns if a 2D draft has uncalibrated dimensional measurements (mapping will require calibration) or if the plan duplicates an existing takeoff on the same source. The linked session then shows Measured in Quantos · linked {date} by {name} in the project, so its origin and link date stay visible.

The draft rules differ by source:

• 2D drawings: scratch → saved draft → linked session → mapping. Mapping and estimate generation require linking first. Saved sessions retain each page’s calibration.
• IFC models: you can map element types/groups in a saved draft before linking. Those mappings and identities survive linking. Estimate generation still requires a project. There is no local 3D scratch-measurement journal.

A linked manual session can move to another project only while it has no mappings; an IFC session must also have no generated estimate. Agent-origin sessions remain in the project that received them. Once the work is mapped, treat its project association as part of its evidence.

Work With a Project 2D Session

Use a project 2D session for a PDF or image that needs durable takeoff.

1. Open the project’s QTO Sessions area and start or resume the 2D session.
2. In Takeoff, calibrate the scale against a known dimension for each drawing page you measure. A dimensional page (one with area, rectangle, or linear measurements) must have a positive scale calibration before the session can be reviewed.
3. Draw or edit areas, rectangles, linear measurements, counts, annotations, or auto-count results.
4. Confirm the autosave indicator reports Saved.
5. Switch to Mapping and connect measurements to the appropriate module or material.

Takeoff edits and mapping edits are saved separately. A Saving indicator means Darwin is still persisting work. An Error indicator means the latest save failed, so the unsaved edits remain only in the current browser session until saving succeeds.

Measurement types are not all equal: area, rectangle, linear, and count are real measurements that can be mapped and generated into an estimate. Annotations are on-drawing notes only — they cannot be mapped or used for quantities.

Review Agent-Driven (OpenTakeoff) Sessions

Some QTO sessions are produced by an external estimation agent rather than drawn by hand. Agent-origin sessions start as Pending Review and are not trusted until a human reviews them: Darwin refuses to generate an estimation or use their mappings in an estimate until the session is reviewed.

• The review status is derived per content revision: NotRequired, Pending, or Reviewed.
• Review the agent’s takeoff and mappings, then mark the session reviewed.
• Editing or recalibrating a reviewed agent session bumps its content revision and resets the session back to Pending — the review is about the current content, not a past pass.

Treat agent output the same way you would treat any other source: check it before it becomes an estimate.

Work With a Project IFC Session

Use a project IFC session when a 3D model needs to generate estimate quantities.

1. Start an IFC import from the project’s QTO Sessions area and upload the .ifc file.
2. Review the import session while it is In Progress.
3. Map each layer in bulk to an existing module, a new module, or a material.
4. Add an individual element override only when the layer needs an exception.
5. Generate the estimation after the mappings are ready.

An individual override changes that layer from bulk mapping to individual mapping. When generation succeeds, Darwin creates an IFC-generated estimation and marks the import session Completed.

Measure on a Model’s Storey Plan

Model-plan takeoff lets you measure an identified storey in an IFC session, alongside quantities obtained from element mapping.

1. Save the model as a draft or project session before capturing plan measurements.
2. Open a verified, identified storey plan and use count, linear, area, or rectangle tools.
3. Map each measurement to a module or material, or explicitly ignore it.
4. Save the takeoff before generating or applying it to an editable estimate. Link a draft to a project first.

The scale comes from the IFC model’s declared units; you do not calibrate it like a PDF. Changing the viewing cut height does not change the stored measurement plane. Unidentified levels and unverified sources remain view-only.

If the same target already receives quantities from IFC mapping in that session, Darwin requires a reason acknowledging the possible overlap. Changed mappings can require a fresh acknowledgement. No warning does not prove that the quantities do not overlap. Element picking/snapping and automatic model-replacement handling are not part of this workflow.

Completed or archived sessions, and sessions supporting approved/finalized estimates, are read-only. A new IFC upload creates a new session; Darwin does not infer replacement from the filename or migrate old measurement geometry automatically.

Use Quantities in the Estimate

Project-backed mappings make quantities available in Estimation Details. Drawing mappings can target an existing module, a material, or a new module, or remain unmapped/ignored. Model-plan mappings target existing modules/materials or are unmapped/ignored; resolve or ignore them before generation.

Drawing quantity = calibrated quantity × multiplier. Model-plan quantity = native quantity × multiplier by default, with supported conversions only when explicitly requested. Check measured and target units yourself: accepted QTO mappings are not automatically dimension-checked or converted. See Units of Measure.

Review Every Quantity Contributor

An estimate line may combine manual quantities, IFC elements, drawing QTO, and model-plan QTO. Its accepted contributor breakdown keeps the source, quantity, units, multiplier/conversion, reviewer, and time for each input; model-plan inputs also keep the storey and accepted geometry. The original measurement is not rewritten when you adjust a quantity manually in the estimate.

Applying the same session again replaces that session’s prior share, rather than adding it twice. Other sessions and manual adjustments remain intact, and superseded applications stay in history. Cloning an estimate preserves this evidence.

Some older lines have only partial source history (LegacyPartial). Darwin does not invent their missing contributors or guess which quantity to replace. Review/rebuild an affected line in an editable estimate before reapplying a session. Review sources before approval, particularly after a design revision or agent-generated takeoff.

Next Steps

• ➡️ Map Elements to Modules
• ➡️ Build the Estimate