Polygons

1. What is the minimum / maximum area of a polygon?

The area of a polygon should be at least 1 hectare and not more than 3,000 hectares.

2. What happens if I create a polygon that is greater than or less than the specified minimum / maximum area limit?

You will receive an error message in API response. So, please be careful with the limit.

3. Is it possible to create a new polygon if I have already reached the available limit of my tariff?

Yes, it's possible. At the end of the billing period, we will send you an invoice that you can pay by Wire transfer or credit card or debit card via Stripe. If we do not receive your payment, we will suspend your account. Limits of your tariff you can find here.

4. What is a format of data is used to specify the polygon?

GeoJSON format is used to specify the geometry of the polygon. Please note that the coordinates of the points have the following order - longitude, latitude. You can learn more about this format in the RFC specification.

5. How do you calculate the total area of the polygons? For example, I can load 100 polygons, but query only one of them.

The total area includes all polygons that you have created in the system. For example, if you create 100 polygons but only query one of them, our system still calculates that you have 100 polygons. That is, all polygons you create are relevant, even if you do not query them.

6. The number of pixels in the current polygon with satellite Sentinel-2 differs from the number of pixels in the same polygon with satellite Landsat 8. Why?

The difference in pixel quantity based on different scale (resolution) of Landsat-8 and Sentinel-2 (nominal value is 30 for Landsat and 10-20 for Sentinel – based on channel). However, in the moment of loading images in our platform we transform data from the original system of coordinates and projection (basically zonal UTM projection) into cylindrical Mercator projection (web Merkator), and cut data into tiles according to the standard tile scheme. In this case maximum scale (zoom level) for Sentinel=14 (one pixel=9.547m), for Landsat=13 (one pixel=19.093m). More details can be found here. Please take into consideration that it is not correct to count the area size depending on these pixels.

Satellite imagery API

1. How do we process satellite imagery

Please read the article 'How do we process satellite imagery so that customer can operate with Ready-to-use Data' in our Blog.

2. I tried to fetch past one month historical NDVI data for my polygon, I was hoping to see 30 records, but in turn there were only several records. Why?

We are using data of two programs: Landsat-8 (one satellite) and Sentinel-2 (2 satellites). According to the documentation of Sentinel-2 periodicity of scanning depends on the latitude and vary from 3 to 5 days. For Landsat-8 periodicity is 16 days. Moreover, if you use free account, our database will not load scenes with cloudiness more than 0 percent. For paid subscriptions we download almost all images, and it gives more details.

3. What are the default value and the best value for resolution_min/ resolution_ma (px/meters), clouds_max, coverage_max?

Minimum resolution for Sentinel-2 = 10m, Landsat 8 = 30m. By default, there are no limitations on cloudiness and coverage. Best possible values are < 5% for cloudiness and 100 for coverage.