Field PracticeWith all these good ideas we set out to implement a national crop survey with NaCRRI this year. The purpose is to test the mobile survey system that automatically updates an online map with survey data from the field in real time. As is always the case the theory underestimates the praxis – this case was no different, several issues we thought were significant and would be problematic actually turned out to be non-issues – this was the good part; the terrifying part were the non-issues that became issues. I detail several of these here spanning from the preparation, training and deployment phases of the apps on the phone and what was observed on two separate field test visits with the actual survey experts.
- Space/storage considerations on the phone – the image capture application uses the native phone camera application. We found that the default setting for the size and resolution of the images taken with the camera had to be changed from a 3M high-resolution image to a 1 M normal resolution image. The size of the images affects how much bandwidth will be used in uploading the images to the server and the capacity of the memory card to use in the phone. For the survey we expect each phone to take a minimum of 1000 images. So for the 8 phones we are using, approximately 10000 images.
- Screen/keyboard size of phone – during the training of the surveyors, the issue of usage of the phone keyboard came up. We are using the Huawei Gaga U8180 which has a display size of 240 X 30 px so its not all that big but still usable with some training. Issues of how to use the touch screen with dirty fingers (from digging up roots, etc.) also came up.
- Sun glare – this happened to be one of the most daunting issues. Collecting data in the gardens when the sun is all out was problematic because of difficulty in seeing the phone screen and hence difficulty in navigating the form. One solution round this was to set the brightness setting to auto on the phone. Some improvement is realized but this is something to take into consideration when buying more devices in the future.
- Background clutter – for one of the field visits we tried to use a cardboard paper that was put behind each leaf before the photo of the leaf was taken. This was a very cumbersome procedure especially when trying to take an image of the whiteflies on the leaves because for the whitefly shot one needs to turn the leaf over as the whiteflies reside on the underside of the leaf. Taking the shot with the background required at least two people to execute. This was rejected and so images have to be taken with a cluttered background and the filtering done at the server end.
- Image capture – To score the severity of disease manifested by a plant accurately some diseases require that the examination of the whole plant is done, while for others this can be done from looking at the canopy of the plant. A 2D image of a plant unfortunately does not provide all the information for accurately determining the severity score of a plant – we thus had to settle with taking two representative images of the plant – one full plant image and a close-up canopy/leaf shot.
- Power/charging issues – the Huawei Gaga like most touch screen phones has about 1 day lifespan on the battery under heavy usage. We had to provide car chargers to the surveyors so the phones could be charged in the cars as they move from one garden to the next.
- Server issues – Google App Engine can only support up to a limited amount of data storage and access for free. We had to enable billing to support this survey of an estimated 10000 geo-coded images.