Sun hotspot in a camera frame
Whether the hotspot, the bright patch where the camera looks straight away from the sun, falls in a camera's frame for its heading and pitch at a place and time, and how far off it is.
The hotspot is 16.3° from where the camera points: in frame, yes.
- The hotspot is 16.3° from the look direction, inside the 84° field of view: expect a bright patch where the drone's own shadow falls, which can upset image matching. Fly earlier or later, or tilt the camera.
- Hotspot in frame
- Sun elevation
- Sun azimuth
- Antisolar azimuth
- Antisolar elevation
Provenance
- Computed by
- time.sun.hotspot 1.0.0, core 0.1.0
- Model
- Sun azimuth and apparent elevation by the NREL SPA (standard atmosphere, sea level); the antisolar point is opposite the sun, at −elevation. The hotspot angle is the angle between the camera's look vector (heading, pitch) and the antisolar direction; it is in frame when within half the diagonal field of view
- Accuracy
- Sun direction to about 0.0003°; the frame test treats the field of view as a cone around the look direction, so a hotspot near a frame corner is borderline
- Notes
- 1 shown with the answer
- Cites
- Reda, I., and Andreas, A., National Renewable Energy Laboratory, Solar Position Algorithm for Solar Radiation Applications (NREL/TP-560-34302)
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: Sun azimuth and apparent elevation by the NREL SPA (standard atmosphere, sea level); the antisolar point is opposite the sun, at −elevation. The hotspot angle is the angle between the camera's look vector (heading, pitch) and the antisolar direction; it is in frame when within half the diagonal field of view
Show your work
Antisolar point
opposite the sun: azimuth + 180°, elevation × −1sun at 178.5°, 73.7°= 358.5°, -73.7°Angle from the look direction
camera 0°, -90°= 16.3°
The same steps an agent gets from the MCP server with explain: true.
Accuracy: Sun direction to about 0.0003°; the frame test treats the field of view as a cone around the look direction, so a hotspot near a frame corner is borderline
When to use this: Use this before an aerial survey to find out whether the hotspot -- the blown patch where the camera looks straight away from the sun -- will land in frame, and how far off it is. Check a planned time and camera attitude, or walk the day to find when the sun is high enough to keep it out.
Limitations: The frame is treated as a cone around the look direction, so the test is exact at the corners and slightly generous at the edges: a hotspot just outside the cone could still clip a corner. The hotspot is a direction, not a brightness -- how bad the patch actually looks depends on the surface, the sun angle and the camera, none of which are inputs here. And a nadir camera catches the hotspot whenever the sun is below about 48 degrees with the default field of view, which is most of a working day outside high summer; that is the geometry, not a fault in the flight plan.
Worked example: A nadir camera at noon near the June solstice in Denver. Source: NREL SPA sun position; with the sun near 73° up, the antisolar point is 17° off nadir, inside an 84° field of view. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.
You enter
- Camera pitch
- -90 deg
- Latitude
- 39.74 deg
- Longitude
- -104.99 deg
- Time
- 2026-06-21T13:00-06:00
You get
- Hotspot off the look direction
- 16.3°
- Hotspot in frame
- yes
- Sun elevation
- 73.7°
- Sun azimuth
- 178.5°
- Antisolar azimuth
- 358.5°
- Antisolar elevation
- -73.7°
Review: Not yet independently reviewed by a geodesist.
Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.0, core 0.1.0. See this tool in the verification report.
Checked against: 23 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- Solar Position Algorithm for Solar Radiation Applications (NREL/TP-560-34302), Reda, I., and Andreas, A., National Renewable Energy Laboratory, Revised January 2008. Sections 3.1 to 3.15 and Tables A4.2, A4.3; worked example in Table A5.1. Read free.