If you don’t find the information you require, please do not hesitate to contact the helpdesk.
Q: How to cite data derived from the ENDELEO monitoring website?
A: Please cite as follows
ENDELEO. Description of the data product. Retrieved MM DD, YY from http://endeleo.vgt.vito.be/.
Figure 1: NDVI of the year 2000 compared with the 10-year average (1998 – 2008) (obtained from ENDELEO).
...the vegetation dynamics were derived from ten day interval NDVI from the SPOT‐VEGETATION sensor. This data was obtained from ENDELEO...
ENDELEO. NDVI of the year 2000 compared with the 10-year average (1998 – 2008) for Mount Kulal. Retrieved June 21, 2008 from http://endeleo.vgt.vito.be/.
Q: How to know what I am downloading or examining?
A: Each ENDELEO data product is accompanied by a product specification sheet. This file contains all information about the data content, used abbreviations, data quality, used attributes, used spatial reference system, etc of the corresponding data product. Before downloading any data product or before starting analysis based on ENDELEO data, please always consult the product specification information. The product specification sheets are downloadable together with the corresponding data product on the ftp-site and are available on this website under the section ‘Help > Data Products’.
Q: What is the difference between the SPOT-VEGETATION and TERRA-MODIS sensor?
A: The ‘Vegetation health & density’ (NDVI) and the ‘Vegetation growth rate’ (DMP) are calculated with the same formula for both sensors and should therefore give a similar result. However, the spatial resolution of the sensors differs. The resolution of the SPOT-VEGETATION is 1km whereas TERRA-MODIS has a resolution of 250m, revealing more spatial detail. Furthermore, the MODIS-TERRA indicators is at this time only processed for a few years, which does not allow to compare the ‘current’ indicator with the ‘average condition’.
Q: Which 'indicator' is most suited for my analysis?
The NDVI evaluates the relative presence (or absence) of healthy, green vegetation, by simply measuring and comparing the spectral response measured by remote sensing instruments. The DMP determines the vegetation growth rate or dry matter productivity by combining measurements from remote sensing instruments with meteorological data.
The NDVI can be used to monitor all kinds of vegetation. The DMP is particularly interesting for cultivated land, where it gives an indication of the yields to be expected, and rangelands, to asses whether the grassland is can support the cattle.
Q: Where do the different types of indicators stand for?
The ‘current’ product exists of a composite of 10 daily images. Single day images are often partly covered by clouds, resulting in an amount of missing values. Combining 10 consecutive images allows to fill most of these gaps. To obtain a composite, for each individual pixel, the highest value within that period is retained.
Over the course of the growing season, the values of the vegetation indicators vary. The ‘comparison to previous 10 days’ is calculated from the difference between the current and the previous vegetation indicator and reveals if the indicator is increasing or decreasing.
The values of the indicators for the same period of the year may also differ between different years.. The ‘comparison to last year’ is calculated from the difference between the current vegetation indicator and the vegetation indicator of the previous year for the same period of the year. However, this comparison does not specify whether in the current or previous year exceptional conditions occurred. For every period of the year, the ‘average condition’ (or ‘long term average’) is calculated. Each pixel of the ‘average condition’ contains the mean value since 1999 for that period in time. The ‘average condition’ reflects the condition that normally occurs and is considered as a reference.
Q: Are the values of the indicators indisputable?
A: The indicators should be interpreted in an intelligent way. Conclusions should not be based on the indicators of a single period in time. For example, sometimes clouds are not well detected by the system and can be wrongly interpreted as poor vegetation conditions. It is recommended to compare the indicators of the current and the previous period(s). If an inferior or superior situation persists over a longer time span, it is more likely to be correct. The statistical graphs are also a useful tool to compare several periods in time.
Q: I am not able to overlay vectors or other data on the images I downloaded from the ENDELEO-ftp.
A: The images are projected in the Kenyan national projection system, Arc1960 UTM37S.
Arc 1960 UTM37S
Projection type: Transverse_Mercator
Linear Unit: Meter (1,000000)
If your software does not recognize the coordinate automatically, you should define it yourselves. If the Kenyan system is not present in the available projection systems, you should create a new projection system with the parameters above.
In ArcMap you define the projection as follows:
Select the ‘define projection’ toolbox (under ‘data management tools’ > ’projections and transformations’).
Click on the button next to ‘coordinate system’.
Click on ‘select’.
Choose ‘projected coordinate systems’ > ‘UTM’ > ‘Other GCS’ > ‘ARC 1960 UTM 37S.prj’.
A manual is available on the ftp-site on how to define the projection system in ArcMap.
Q: I get an error when opening the images from the ENDELEO-ftp, saying the projection system is not defined.
A: see previous answer
Q: How are the filenames from the ENDELEO-ftp build up?
A: The filenames are build up as follows
A : sensor type
Mt = MODIS-TERRA
Vt = SPOT-VEGETATION
B: period covered
t = dekad (10 days)
m = month
e.g. 09 = 2009
DD: number of the decade if S10/ number of the month if S30
e.g. 04 = first part of February for S10
e.g. 04 = April for S30
(x): in case of quicklook
i = NDVI quicklook
p = DMP quicklook
NDVI = vegetation health and density
DMP = vegetation growth rate
EE: compared to…
dd = previous 10 days
dh = average conditions
dy = previous year
Q: How are the foldernames from the ENDELEO-ftp build up?
A: The foldernames are build up as follows
AAA = indicator
NDVI = Vegetation health and density
DMP = vegetation growth rate
BBB= difference with...
HIS = average conditions
YEAR = previous year
QLK = quicklooks
S10 = decadal images
S30 = monthly images