Convert magnetic bearing to true bearing for dish pointing
A satellite dish must be aimed at two angles: azimuth around the mast and elevation above the horizon. A number that looks plausible can still miss a narrow satellite beam, so the reference direction matters as much as the arithmetic. SatPointer supplies the geometry; the installer must still interpret it at the actual dish.
Compasses normally indicate magnetic north, while orbital calculations use true north. Between those references sits declination, also called magnetic variation. Its size and direction depend on location and change over time, which makes a bearing copied from another Australian city unreliable.
SatPointer combines Google Maps, a selected satellite and orbital data to produce pointing directions for reception, uplink, downlink and mobile links. For a standard installation, enter the site, select the satellite and read the calculated azimuth and elevation. The true azimuth is the value against which a calibrated compass reading must be compared.
Using the site does not replace signal testing, compass calibration or safe rooftop work. Its value is consistency: it turns the site address into a repeatable reference and helps prevent the common mistake of adding magnetic variation twice.
Bearing references and satellite pointing
Satellite azimuth is an angle measured clockwise from a chosen north direction. Magnetic bearings begin at magnetic north, which is where a conventional compass points; true azimuth begins at geographic north. Grid bearing, common in maps and survey work, uses the projection’s central meridian and therefore differs again. Confusing these references shifts the aim even when every other setting is correct.
The references can be compared as follows:
| Bearing type | Zero direction | Where it is used |
|---|---|---|
| Magnetic bearing | Magnetic north | Conventional compass readings and compass calibration |
| True bearing or azimuth | Geographic true north | Satellite orbital geometry and precise dish coordinates |
| Grid bearing | Grid north for the map projection | Surveying, mapping and some engineering plans |
SatPointer reports true pointing geometry for the chosen site and satellite. If an installer gives a magnetic bearing, convert it to a true bearing before comparing it with the target. If the program already displays true azimuth, do not apply declination a second time.
Why Australian locations change the answer
Across Australia, declination ranges from westerly near Perth to easterly across much of the continent. Recent magnetic models place Sydney and Melbourne near 13° east, Brisbane around 11° east and Adelaide around 9° east, while Perth is roughly 2° west. These are rounded orientation values, not substitutes for the date-specific value at your site.
That spread means the same magnetic reading can produce quite different true azimuths. An east-positive offset of 13° changes a 090° magnetic bearing to about 103° true. At a western site, a westerly offset moves the number in the opposite direction. A small error can matter because many geostationary beams are narrower than a casual visual estimate.
Regional geology, longitude and the magnetic field’s gradual drift all contribute. Field equipment, a steel roof and a nearby transformer can also distort a handheld compass. Australian installers should therefore record the location and correction rather than reuse a familiar offset from a previous job.
Set the location before calculating
Start with the dish position, not simply the street address. In the SatPointer location control, select or place the site on Google Maps and, where possible, pinpoint the actual mount. A rooftop installation in Sydney may have a different horizon from a nearby ground-level installation even when both share a suburb.
Site elevation and orbital geometry feed into the elevation solution, while nearby buildings, trees and hills can block a low line of sight. Note obstructions before moving the mast. The site’s satellite database can then be used to check the selected spacecraft’s beam coverage, orbital position and estimated dish size before ordering hardware.
For a manual conversion, obtain the magnetic declination for the exact coordinates and check its date or magnetic-model epoch against an authoritative source. Keep magnetic north, true north and grid north separate in your notes. SatPointer’s direct azimuth removes the need to perform this step, but knowing the conversion helps verify a contractor’s compass reading.
Read and apply the SatPointer result
Open SatPointer’s direction analysis and choose the installation location. Select the intended satellite and link type—reception, uplink, downlink or mobile—and allow the calculation to use the current orbital geometry. Its role is to determine where the spacecraft appears from your coordinates, not merely to copy a generic compass direction.
Read the resulting true azimuth as a clockwise angle from true north, and read elevation as the height of the satellite above the local horizon. For geostationary services over Australia, elevation will be relatively high, but the exact value still changes with latitude and orbital longitude. Make sure the selected satellite carries the channel or frequency you intend to receive.
Compare the result with an existing installation before loosening anything. An offset dish also needs the correct feed-arm or LNB skew for circular polarisation, and small feed-arm angles can be confused with azimuth error. A calculation gives the ideal pointing position; it cannot compensate for a crooked mast, loose bracket or damaged cable. Installers can also embed a SatPointer widget on a website so customers can generate a pointing result for their own address.
Convert a magnetic reading with declination
Use east as positive and west as negative. The working relationship is: true bearing = magnetic bearing + declination. With a site-specific declination of 13° east, a magnetic bearing of 090° becomes 103° true. If declination is 2° west, treat it as −2°; a magnetic reading of 270° becomes 268° true.
The reverse conversion is magnetic bearing = true bearing − declination. A chart showing 13° W means subtract 13°, while 13° E means add 13°. Always check the direction letter and sign. Grid convergence is a separate correction used with grid bearings, so it should not be combined with declination unless both north references are handled deliberately.
This reverse calculation matters at the dish. A conventional compass is still zeroed on magnetic north, so a true target of 103° in an area with 13° easterly declination appears as 090° on that compass. Use the magnetic equivalent when setting an uncorrected compass, and use true azimuth for documentation and comparison.
For a practical check, write down the magnetic reading, apply one signed correction, then compare the result with SatPointer’s true azimuth. Use the live site value rather than a rounded city example. Keep the result to at least one decimal place for planning, then make final adjustments from receiver signal-quality readings.
Plan a compliant and practical installation
Receiving-only satellite television installations and transmitting earth stations sit within Australia’s radio-frequency framework. The ACMA administers licensing under the Radiocommunications Act 1992, and licence-exempt receiving equipment has conditions; uplink or mobile transmit systems may require appropriate permissions. Confirm the regulatory class before fitting an active transmit antenna rather than assuming consumer reception rules cover every link.
Local site rules still apply. Owners or body corporators may regulate roof access, shared cables and communal areas, and a heritage overlay can affect a visible structure. In suburban backyards, installers also work around roller doors, rainwater tanks, pools and covered patios. Use approved brackets, weather-seal cable entries and a stable mast, and have a licensed electrician handle mains-connected equipment where required.
A practical mobile example is the Stellat alignment example, which shows how a real satellite task can be approached. Australian households may choose Foxtel for a fixed dish or Starlink for a self-aligning array, while farms, mines and transport operators use larger Ku- or Ka-band systems. Proprietary arrays need their own commissioning process, even when SatPointer is useful for wider direction planning.
Align the dish and confirm the signal
Before loosening the dish, make the site repeatable and the references explicit.
Practical alignment checklist
- Record the exact coordinates, selected satellite, intended frequency and link type.
- Use SatPointer’s true azimuth for comparison, converting it back to magnetic when setting an uncorrected compass.
- Calibrate the compass away from steel, vehicles, power wiring and the dish mast; compare at least two devices if possible.
- Set azimuth in small increments, then adjust elevation and LNB skew while watching signal strength and quality.
- Photograph the final settings and note them, making later maintenance or realignment easier.
Keep the dish unobstructed and allow it to settle before tightening. Check the signal at the receiver or meter, including picture lock, BER or C/N figures where available. Heavy rain, foliage and nearby construction can change performance, so a momentary peak should be confirmed over a normal viewing period.
Open SatPointer, enter the Australian installation address, choose the satellite and save the calculated true azimuth before the installer arrives. Use that value as the shared reference for the site visit, then confirm reception at the receiver for a confident handover.