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substantially from a larger dataset. |
Restricted set of questions: |
While not appearing in the numerical evaluation, an important |
issue with our results is the relative lack of diversity in the |
dataset. Indeed, due to the source of our data (OSM), the |
questions are only on a specific set of static objects (e.g. |
buildings, roads, . . . ). Other objects of interest for applications |
of a VQA system to remote sensing would also include differ- |
ent static objects (e.g. thatched roofs mentioned in section I), |
moving objects (e.g. cars), or seasonal aspects (e.g. for crop |
monitoring). Including these objects would require another |
source of data, or manual construction of question/answer |
pairs. |
Another limitation comes from the dataset construction |
method described in subsection II-A. We defined five types |
of questions (count, comparison, presence, area, rural/urban |
classification). However, they only start to cover the range of |
questions which would be of interest. For instance, questions |
about the distance between two points (defined by textual |
descriptions), segmentation questions (e.g. ”where are the |
buildings in this image?”) or higher semantic level question |
(e.g. ”does this area feel safe?”) could be added. |
While the first limitation (due to the data source) could be |
tackled using other databases (e.g. from national institutes) and |
the second limitation (due to the proposed method) could be |
solved by adding other question construction functions to the |
model, it would be beneficial to use human annotators using |
a procedure similar to [5] to diversify the samples. |
V. C ONCLUSION |
We introduce the task of Visual Question Answering from |
remote sensing images as a generic and accessible way of ex- |
tracting information from remotely sensed data. We present a |
method for building datasets for VQA, which can be extended |
and adapted to different data sources, and we proposed two |
datasets targeting different applications. The first dataset uses |
Sentinel-2 images, while the second dataset uses very high |
resolution (30cm) aerial orthophotos from USGS. |
We analyze these datasets using a model based on deep |
learning, using both convolutional and recurrent neural |
networks to analyze the images and associated questions. The |
most probable answer from a predefined set is then selected. |
This first analysis shows promising results, suggesting the |
potential for future applications of such systems. These re- |
sults outline future research directions which are needed to |
overcome language biases and difficult tasks such as counting. |
The former can be tackled using an attention mechanism [24], |
while the latter could be tackled by using dedicated compo- |
nents for counting questions [33] in a modular approach. |
PRE-PRINT. FINAL VERSION IN IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 11 |
0654402298022025162754True |
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(a) Test set 1 |
0654402298022025True |
PredictedYesNo0m²1m² - 10m²10m² - 100m²100m² - 1000m²1000m²+012345678910 |
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(b) Test set 2 |
Fig. 11. Subsets of the confusion matrices for the high resolution dataset (counts are at logarithm scale) on both test sets. Red lines group answers by type |
(”Yes/No”, areas, numbers). |
Fig. 12. Evolution of the accuracies (evaluated on the first HR test set) after |
training with subsets of different size of the HR training set. |
Issues regarding the current database raised in section IV |
also need to be addressed to obtain a system capable of |
answering a more realistic range of questions. This can be |
done by making the proposed dataset construction method |
more complex or by using human annotators. |
ACKNOWLEDGMENT |
The authors would like to thank CNES for the funding of |
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