1. Overview
The Measure tab measures distances and areas directly on the loaded image. Every result is always reported in pixels, and, once a scale is set, also in real-world units such as metres, kilometres, feet or hectares.
Key points
- Seven drawing tools: three for distance (Line, Path, Freehand) and four for area (Rectangle, Ellipse, Polygon, Freeform).
- The scale can come from the file itself (Auto), be typed in (Custom), or be left off (Pixels).
- Horizontal and vertical scales are independent, so non-square pixels are measured correctly.
- Changing the scale or display unit updates every existing measurement instantly. You never need to redraw.
- All measurements can be exported to CSV with both pixel and real-world values.
Availability: Starter tier and above. A file or satellite scene must be loaded.
2. What the Measure Tab Does
1. Draw a distance line or an area shape on the loaded image. The viewer stores its points in image pixel coordinates.
2. It calculates length, area, and perimeter in pixels; an active scale also converts them to physical units.
3. Read the values on the image and in the Measurements panel, or export the results as CSV.
Measurements are stored in image pixel coordinates, not screen coordinates. Zooming, panning or resizing the window never changes a result.
3. Where to Find It
1. Load a file from My Files / Upload & View in the sidebar, or load a scene from the Satellite Data page.
2. Click Measure (ruler icon, teal) in the top toolbar.
3. The scale bar appears above the image, the drawing toolbar sits directly on top of the image, and the Measurements panel appears on the right.
4. The ? icon at the top-right corner of the scale bar opens this documentation in the in-app Help page.
4. Screen Layout
Area
Location
What it contains
Scale bar
Above the image
Scale mode (Pixels / Auto / Custom), pixel-size inputs, display-unit dropdown
Drawing toolbar
Top of the image pane
Pan, the seven drawing tools, Undo, Clear all, and a hint for the active tool
Image pane
Left, resizable
The current view with measurements drawn over it; zoom buttons top-right; status strip bottom-left
Status strip
Bottom-left of the image
Current scale (e.g. 1 px = 10 m), zoom level, and warning badges (Approximate scale, No georeferencing in this file)
Data Info
Top of the right panel
Cube dimensions, wavelength range, source, Export and Metadata buttons
Measurements panel
Right, resizable
One card per measurement, plus the CSV export button
Drag the vertical handle between the image and the right panel to resize them.
5. Step by Step Workflow
Step 1 Open the tab
Load a scene and click Measure in the top toolbar.
Step 2 Set the scale
In the scale bar, choose
- Pixels to measure in px / px² only (default).
- Auto to use the pixel size stored in the file (GeoTIFF, ENVI with map info, or a satellite scene). The button is greyed out when the file has no georeferencing.
- Custom to type the ground size of one pixel yourself.
You can set or change the scale at any time, before or after drawing.
Step 3 Pick a tool
Click a tool in the drawing toolbar. Distance tools highlight in teal and area tools in amber. The hint on the right side of the toolbar explains how to draw with the selected tool.
Step 4 Draw on the image
- Drag tools (Line, Rectangle, Ellipse, Freehand, Freeform): press, drag and release.
- Click tools (Path, Polygon): click each vertex, then double-click or press Enter to finish.
Each new measurement is labelled M1, M2, M3… and gets its own colour.
Step 5 Read the results
Every measurement appears as a card in the Measurements panel, showing pixel values on the left and scaled values on the right (highlighted in teal). Click a card to select that measurement and highlight it on the image.
Step 6 Refine or remove
- Undo (↶ button or Ctrl+Z) removes the most recent measurement.
- Select a measurement and press Delete to remove just that one, or hover its card and click the trash icon.
- Clear all (trash button in the toolbar) removes every measurement.
Step 7 Export
Click CSV in the Measurements panel header to download measurements.csv. The measurements table is also offered in the Export dialog (Data Info panel) so it can be saved to your computer or to a cloud folder along with other results.
Navigation
Pan
Drag the image with the left mouse button
Drawing is paused while Pan is active. Only useful when zoomed in, because at 1× there is nothing to pan.
Distance tools
Line
Drag from start to end
Straight-line distance between two points
Path
Click each point; double-click or Enter to finish; Backspace removes the last point
Total length of a multi-segment path (sum of all segments)
Freehand
Drag to trace any curve
Length of the traced line. Points closer than 1.5 px are merged to remove mouse jitter.
Area tools
Rectangle
Drag corner to corner
Area and perimeter of an axis-aligned rectangle
Ellipse
Drag a box; the ellipse fills it
Exact area π·rx·ry and a high-accuracy perimeter
Polygon
Click each vertex; double-click or Enter to close; Backspace removes the last vertex
Area (shoelace formula) and perimeter including the closing edge. Needs at least 3 vertices.
Freeform
Drag to enclose any shape
Area and perimeter of the traced outline
The area tools are the same set used in Machine Learning → Labeling, so they behave the same in both places.
7. Scale Settings
Scale modes
Mode
What it does
When to use
Pixels
No conversion. Lengths in px, areas in px².
Relative comparisons, or when the ground size is unknown
Auto
Reads the ground pixel size from the file's georeferencing. The source is shown in the bar (e.g. GeoTIFF, ENVI map info, Satellite scene bounds) with 1 px = X × Y.
Georeferenced GeoTIFF / ENVI files and satellite scenes
Custom
You enter the size of one pixel.
Lab or microscope images, drone imagery with a known GSD, or any image with a known reference size
Where Auto gets its scale
Source
Accuracy
How it's derived
GeoTIFF
From file metadata
Affine transform and CRS of the file
ENVI map info
From file metadata
The map info line of the .hdr header
Satellite scene bounds
Approximate (badge shown)
The scene's bounding box ÷ image rows/cols, converting degrees to metres at the scene's mid-latitude
Custom scale options
Same both axes (toggle)
On (default): one input drives both axes (square pixels). Off: separate horizontal (across / east-west) and vertical (down / north-south) inputs.
1 px = [value] [unit]
Ground size of one pixel. Must be a positive number. Units: nm, µm, mm, cm, m, km, in, ft, yd, mi.
Units can differ between the axes. For example, 1 px across = 0.8 km and 1 px down = 5 m is valid.
Display unit
Auto (best fit)
Lengths use the largest of km / m / cm / mm that keeps the value ≥ 1. Areas use mm², cm², m² or km² depending on size.
A specific unit
Forces every length into that unit and every area into its square (e.g. ft → ft²).
The display unit only changes how numbers are shown. It is disabled while the scale mode is Pixels.
8. Output and Interpretation
Measurement card
Field
Distance measurements
Area measurements
Header
Colour swatch, tool icon, label (M1…), distance, number of points
Colour swatch, tool icon, label, area, number of vertices
Left column
Length in px
Area in px², Perimeter in px
Right column
Length in real units (— when no scale)
Area and Perimeter in real units (— when no scale)
When no scale is active, a notice at the top of the panel reminds you that results are in pixels.
CSV export
measurements.csv starts with two comment lines recording the display unit and the scale used, followed by one row per measurement:
type
line, path, freehand, rect, ellipse, polygon, freeform
vertices
Number of stored points (0 for ellipses, which are stored analytically)
length_px
Path length in pixels (distance tools)
area_px2
Enclosed area in square pixels (area tools)
perimeter_px
Boundary length in pixels (area tools)
length_m, area_m2, perimeter_m
The same values in metres / square metres. Blank when no scale is set.
Real-world columns are always in metres in the CSV, whatever display unit is selected, so spreadsheets receive consistent numbers.
9. Keyboard and Mouse Reference
Left-drag
Draw with the active drag tool
Left-click
Add a vertex (Path / Polygon)
Double-click / Enter
Finish the current Path or Polygon
Backspace
While drawing: remove the last vertex. Otherwise: delete the selected measurement.
Escape
Abandon the Path or Polygon being drawn
Ctrl+Z (⌘Z on Mac)
Undo the last measurement
Delete
Delete the selected measurement
Mouse wheel
Zoom toward the cursor (1× – 20×)
Right-drag or middle-drag
Pan while zoomed, keeping the left button free for drawing
Zoom buttons (top-right)
Zoom in, zoom out, reset zoom
Keyboard shortcuts are ignored while the cursor is in a text box or dropdown, so typing a scale value never deletes a measurement.
10. How the Numbers Are Calculated
All geometry is computed in pixel space and then scaled per axis. With sx and sy the metres-per-pixel along X and Y:
Segment length
√((Δx·sx)² + (Δy·sy)²)
Path length
Sum of all segment lengths
Polygon area
Shoelace area in px² × sx × sy
Polygon perimeter
Sum of edges, including the closing edge, each scaled as above
Ellipse area
π · (rx·sx) · (ry·sy)
Ellipse perimeter
Ramanujan's second approximation
Auto scale from satellite bounds
sx = Δlon/cols × 111,320 m × cos(mid-latitude); sy = Δlat/rows × 111,320 m
Scaling each axis independently accounts for unequal pixel dimensions under the stated axis-aligned model. This is why non-square pixels are handled correctly.
11. Known Limitations
Measurements reset
They are cleared when a new file is loaded, or when the image is cropped or rotated, because the pixel grid they were drawn on changes. Export to CSV first if you need them.
Satellite scale is approximate
Derived from the bounding box under a locally flat assumption, marked Approximate scale. It is also wrong after cropping. GeoTIFF and ENVI scale accuracy depends on the file metadata and coordinate system.
Large areas
The degrees → metres conversion uses one mid-latitude, so measurements spanning very large north-south distances carry some projection error.
Planimetric only
Distances are measured on the flat image. Terrain relief and sensor tilt are not accounted for.
Session-only
Measurements are not saved with the file. Use CSV export to keep them.
12. Common Use Cases
Field or plot area from satellite imagery
Polygon, Freeform
Auto (satellite / GeoTIFF)
River width, road length, distance between features
Line, Path
Auto
Leaf, seed or sample size in lab hyperspectral images
Ellipse, Line
Custom (from a calibration target)
Lesion, defect or contamination area on a sample
Freeform, Polygon
Custom
Drone imagery with a known GSD
Any
Custom (per-axis if pixels are not square)
Relative size comparison when the scale is unknown
Any
Pixels
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