Slope Profiler

Purpose: Record device-based slope observations along a drawn section.

Before you start: An active project, access to Slope Profiler, working orientation input and a checked location.

Expected result: A station profile that you can export as GeoJSON or add as two project layers.

For a complete practice example, follow Record a slope profile. Its readings and locations are explicitly simulated.

1. What Is the Slope Profiler?

Slope Profiler estimates tilt from your device's orientation input. It combines each recorded angle with a position along a map line to build a station profile. It does not obtain ground slope from satellite imagery or an elevation model.

Use it for preliminary observations and field notes. Device tilt, placement and location affect the result; the walkthrough does not establish measurement accuracy.

2. Activating the Profiler

1. Activate the intended project and open Map.
2. Open Settings → Field tools, enable Slope Profiler, and choose Done. Access is plan-dependent; see Access & requirements.
3. Tap the orange Slope Profiler map button, then Draw Section.

Finish or cancel other drawing and measurement operations first. Slope Profiler has its own station workflow; Quick Capture Mode does not need to be enabled.

Motion permission handling depends on the device and platform. Allow access if prompted. At calibration, gently tilt the device and confirm that the live values change. Before live input arrives, the gauge shows — and WAITING FOR SENSOR. A genuine calibrated zero is a valid reading.

3. The HUD (Heads-Up Display)

During recording, the gauge displays the current signed tilt and grade. Grade is calculated as tan(angle) × 100: for example, 10° is about 17.63%.

Display	How to read it
Angle and grade	The gauge, station list and export preserve the sign of the reading. Color still uses angle magnitude.
Color	A visual band based on angle magnitude, not a terrain classification or acceptance standard.
Profile and station list	Signed recorded values; moving the phone afterward does not change a saved station.

Absolute angle	Color
Below 5°	Green
5° to below 15°	Yellow
15° to below 30°	Orange
30° and above	Red

4. Drawing a Cross-Section

Draw the baseline first

After Draw Section, tap the start point A, then the end point B. Add intermediate vertices if needed. Tap the last vertex again to finish drawing. The calibration screen opens. These map taps create the baseline; they do not record sensor stations.

Record stations along it

After calibration, move from A toward B in a consistent direction. At each station:

1. Check your location and keep the phone's long axis aligned with the surface and direction you intend to measure. Holding it level at every station would measure the level phone rather than the surface.
2. Wait for a stable, responsive reading and choose Record Station.
3. Wait for the station to appear before moving on. Check its distance, signed angle and calculated relative height.

The app projects the location onto the nearest point of the drawn section. If location acquisition fails, it asks before using the map center, labels an accepted fallback Map center (manual), and preserves that source in the export. Cancel leaves the station unrecorded. A station appearing on the line is not proof of a successful GPS fix.

After Use map center, a required Review station quality dialog stays open for a separate decision. Record anyway adds the station once; Cancel adds nothing. Check the station count after recording.

Open Settings in the profile sheet to set optional location accuracy and distance from section limits in metres. Both are off by default: choose limits appropriate to your task and equipment. Exceeding a limit, unknown accuracy with an accuracy limit enabled, or moving back toward A opens Review station quality. Choose Cancel to reposition or Record anyway to retain the observation with quality flags. The backtracking warning is enabled by default and can be disabled for an intentional reverse observation. These are review prompts, not a certification of measurement quality. The settings are saved for the current project on this device. Use Save settings to apply them or Cancel to keep the previous values; keyboard users can Tab between controls and press Escape to close the settings dialog.

Use Undo to remove the most recently recorded station. Record at least two stations, then choose Finish.

5. Calibration

Place the device on a known level reference in the orientation you will use for observations. Check that the live β (front-to-back tilt) and γ (side-to-side tilt) respond, then hold it still and choose Set Zero. The app requires fresh sensor samples before accepting Set Zero. Missing or expired input leaves the existing calibration unchanged. On success, the displayed angle and grade become zero immediately; you do not need another sensor event to apply the offset. The app averages recent samples and subtracts that baseline from subsequent readings; slope uses calibrated front-to-back tilt.

Skip continues with the current offset; it does not establish a new zero. Redo Section discards the current draft geometry and starts drawing again. Cancel Profile discards the unfinished section. Previously completed sections are retained.

6. The Profile Sheet

Component	Meaning
Chart	Choose Slope or Relative height in the chart selector. The chart title identifies Slope (°) or Estimated relative height (m). The horizontal axis uses actual numeric distance along the active section, so unequal station spacing remains unequal on the chart.
Station row	Station number, distance along the section, calculated relative height and signed slope.
Count	Section count plus stations in the current profile; for multiple sections, check the export for the overall station total.
Action bar	Recording controls or, after Finish, Export, Add, New Section and Clear.

The station list becomes compact above four stations. It is displayed in distance order; Undo still removes the last station recorded.

Relative height is accumulated from distance changes and station angles, using zero as the section-start reference. It is not measured altitude. Reversing travel or turning the phone can alter the sign and accumulated result. Review out-of-order stations before exporting.

7. Action Bar

Control	What it does
Draw Section	Start a baseline for a new profile.
Record Station	Save the current angle with a position projected onto the baseline.
Undo	Remove the latest recorded station.
Settings	Set project-specific quality warnings and the maximum reading age.
Refresh	Restart sampling; move the device, return it to the measurement surface and wait for fresh input.
Resume Save	Continue an interrupted Add using its saved snapshot and names.
Finish	Complete a section with at least two stations and retain it in the local profiler session.
Close (×)	Hide the tool and retain its session on this device.
Resume	Reopen an unfinished section, retain its recorded stations and calibration, and restart live sampling. Wait for a new reading before recording.
New Section	Start another baseline while retaining completed sections. An unfinished draft is replaced.
End / Cancel	Discard the unfinished draft while preserving completed sections.
Clear	After confirmation, remove this project's local profiler sections. Previously added project layers and downloaded files remain.

The session is saved locally for the active project. Closing the tool or reopening the app is not a cloud-sync confirmation. Clearing app/browser storage removes this local session and its Add recovery receipts; keep an export or add the data to project layers before relying on it elsewhere.

Continue after Close → Resume

Resume keeps the section, recorded stations and calibration. The live gauge initially shows — / WAITING FOR SENSOR until new orientation input arrives. Check that the reading responds to a change in tilt before choosing Record Station. A recording attempt without a new valid reading is refused with a message; it does not reuse the pre-close angle.

If a location request was still running when you closed the tool, its delayed result will not add a station after Resume. Wait for a live reading and choose Record Station again when ready. SENSOR ACCESS DENIED or SENSOR UNAVAILABLE means you need to resolve sensor access before recording.

Reading age and returning from the background

The live gauge shows the reading age. Maximum reading age defaults to 15 seconds, configurable from 2 to 120 seconds per project. Once it expires, the gauge shows a stale-reading message and blocks both Set Zero and Record Station. A reading can also expire while location acquisition or a quality confirmation is pending; in that case record again with fresh input. Already recorded stations keep their original measurements.

Some devices emit orientation events only after movement. If a stationary reading expires, gently move the device, return it to the measurement surface, then wait for a responsive reading. Refresh restarts access but does not create a measurement. Backgrounding the app clears live readings and cancels pending capture; after returning, choose Refresh. Calibration and recorded stations are retained.

For GPS route recording, see Record Path and Silent Track: a recovered route requires Resume. In Slope Profiler, Refresh restarts live sensor input in an open section, Resume reopens a closed unfinished section, and Resume Save completes an interrupted Add.

Labels and numbers follow the selected English, Arabic, French or Spanish app language, including right-to-left layout for Arabic. Saved numeric values and GeoJSON units remain degrees, metres, percent and milliseconds regardless of display language.

8. Practical Scenarios

For a route review, draw a baseline and record several observations to identify changes that need closer inspection. For a drainage review, keep a consistent phone orientation and station direction, then examine signed angles and spacing. Satellite imagery provides map context only.

The practice lesson demonstrates these controls with fictional inputs; use your own checked measurements for actual field decisions.

9. Export or add the result

Finish, Export and Add are separate steps:

• Finish retains the section in the local profiler session.
• Export downloads a GeoJSON file containing one line per eligible section and one point per station. Sections with fewer than two stations are excluded. The file can include multiple sections, even though the chart shows one profile.
• Add asks for a name and creates two project layers: [name] - Sections and [name] - Stations. For one section with four stations, expect two layers and five features.

The GeoJSON contains longitude/latitude coordinates, section statistics and station properties such as distance_m, slope_deg, slope_pct and elevation_m. Here, elevation_m is calculated relative height. Station exports also retain position_source, position_accuracy_m, section_offset_m, quality_flags, reading_age_ms, freshness_limit_s, quality_accuracy_limit_m and quality_offset_limit_m. Absent historical evidence stays null or unknown. Signed mean slope and mean absolute slope are different statistics: opposing signs can cancel in a signed average.

Open Data & Sync to check both layers and their counts. If Add is interrupted, Resume Save continues with the profile and names saved when Add began, including after reopening the app. One layer can be visible before the other finishes; check both before handing over. A repeated Add of the unchanged completed snapshot verifies the same pair without duplicating it. Adding a changed profile creates a new pair; it does not update the previous pair.

Resume continues an unfinished measurement section; Resume Save completes an interrupted transfer into project layers. It uses the snapshot taken when Add began, so later draft changes are not silently substituted.

Layers created by older versions without an Add recovery receipt are not automatically linked to the new save workflow. Check existing project layers before adding that older profile again.

Finish a pending save before adding another profile. Clear removes profiler sections but keeps a pending Add receipt available through Resume Save; it does not delete project layers. Do not clear app/browser storage during recovery. If recovery storage cannot be written, further layer writes stop. If Add is unavailable in your browser, use the offered GeoJSON export. For a hosted project, verify delivery separately using Data & synchronization.

10. If a reading or result looks wrong

Symptom	What to check
Gauge shows — or a sensor-access message	Wait for live input; check orientation access and device support. Record Station cannot save without a valid reading.
Stations cluster at one distance	Check location acquisition and map-center fallback. Undo incorrect stations and repeat only with a checked location.
Reading becomes stale or the app returns from the background	Use Refresh, move and reposition the device, then wait for fresh input. Review the project reading-age setting if needed.
Add stops with a recovery message	Reopen the profiler and use Resume Save. Check both layers; do not clear browser/app storage.
Finish does not complete	Record at least two stations.
Slope data absent from Data & Sync	Finishing a profile is a local profiler save. Use Add to create project layers.
Added total exceeds station count	Each section line is also a feature; four stations plus one section equals five.

Next: Map PDF Export explains map documents. For the slope measurements themselves, use the profiler's GeoJSON export.