Default Date Ranges valid for USA only
SASHA sets the default date range for your scan by finding the weather station nearest your location, and using that station’s last Spring Frost Date and first Fall Frost Date as the date range. Currently, only continental USA weather stations are available. Currently Sasha provides no warning if it cannot find a nearby weather station.
We are working on providing similar default values for other parts of the world
We are working on issuing a warning if SASHA cannot find a nearby weather station to obtain these default values.
As a work-around, users should always check that the default date range seems reasonable to them, and if not, setting the date range manually.
Reflections can fool SASHA
Sometimes, when SASHA scans white or reflective surfaces, it can confuse those surfaces with open sky or clouds. For example, the reflection of sky in a window looks like sky to SASHA. Similarly, a white surface, such as the side of a white home or shed, looks sufficiently like white clouds to fool SASHA into thinking it is a cloud.
We are working on a way to allow you to exclude such surfaces.
Low plant locations are difficult to scan
In order to get an accurate scan, SASHA must be held as near as practical to the plant whose sun exposure you want to measure. If a plant is very low, this could be challenging!
We plan to allow use of the front facing camera during scans, which will make such low scans easy to achieve.
In the interim, the following work-arounds may help:
- Place a mirror on the ground to allow you to see the screen while you scan the surroundings.
- Lie down on the ground (face up) to do the scan.
Low Light Levels will fool SASHA
SASHA may not produce accurate scans in low light conditions. You should not use SASHA in the dark, or on heavily overcast days. Bright sunny days or lightly overcast days are fine.
Currently, no mitigation is planned.
Compass Inaccuracies can cause poor results
Sasha is only as accurate as the sensors of your device allow it to be. Some devices, for example, have sensors (most notably the magnetometer, i.e. the compass) which are “noisy”. This noise may make the Augmented Reality indicators on your screen “jump around” or “jitter”.
Similarly, the compass is sensitive to all the electrical and magnetic activity inside your device itself. It’s something of a miracle that the compass works at all given all these distractions!
There are several things you can do to minimize these effects:
- Always perform the “figure 8” compass calibration procedure after you start SASHA. See ### for an illustration.
- Always keep in mind where the cardinal directions (North, South, East, and West) are and mentally check that the Augmented Reality indicators are in a “reasonable” place. Often, if the compass needs calibration, it’s WAY off. This happens most frequently when the device has just been turned on, or after it has been sitting around motionless.
- Before you press the screen to take a picture, hold the device still and allow the Augmented Reality indicators “settle down” and find their right place.
Since these inaccuracies are inherent to the devices, and vary from device to device, the SASHA app is unable to mitigate them more than we already have.
- SASHA will not work well near the earth’s poles.
- SASHA has not been tested in the Southern Hemisphere.
- SASHA’s location is only as accurate as that provided by you device.