Our reviewers evaluated the golf GPS devices for two types of accuracy – device accuracy and mapping accuracy. To keep everything on the up-and-up, we did our on-course testing on clear days (no rain, dense clouds or fog) with strong signal strength. We avoided the likes of solar flares, high voltage electricity lines and cell phone towers for good measure, and focused on reception in non-forested areas with no tall buildings nearby.
Keep in mind that you shouldn’t be surprised if your golf GPS device is showing a different distance reading from your partner’s laser rangefinder or a sprinkler head on the course. Laser rangefinders are based on the distance to the hazard or target point in a straight line, regardless of elevation change. GPS devices, on the other hand, are measuring based upon a bird’s-eye view of the hole, so the distance reading assumes there is no elevation change between the player and the target. Therefore, in situations with significant elevation change between yourself and target, the GPS device will give a shorter distance reading than a laser rangefinder.
Some devices do not display distances once the device was within a certain range (up to 50 yards) of a target. This made it difficult if not impossible to determine accuracy based on device readings in some instances.

GPS Chipset Accuracy

Golf GPS chipsets have an accuracy of within 3-4 yards under optimal conditions, with a clear sky and good satellite coverage. During our tests we did not find it possible to differentiate between the devices based on their GPS chipset or software.
While we did not see a difference in accuracy based on the chipset, we could see a difference in how quickly it takes GPS devices to lock into satellites when powering up, how long users need to “pause” after reaching their ball to ensure that the device has updated the distances readings, and also if devices would lose their satellite lock when the device would be put into a pocket or bag during play.

Mapping Accuracy

Golf course mapping accuracy is what sets the GPS devices apart. In general, devices use their proprietary database of location coordinates to generate the distances provided. Depending on the device, courses may be mapped by the device manufacturer, by a third party hired by the manufacturer, or by an end user either on the course or in their home. Depending on which mapping method is employed by the manufacturer, you can wind up with wildly different distance readings.
We compare golf GPS distance readings to course markings, and where there is significant discrepancy between the two, cross check against both a laser rangefinder as well as other dedicated golf GPS devices. We check distance readings for accuracy both throughout our round as well as across different courses.