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answering for remote sensing data (RSVQA). Remote sensing
images contain a wealth of information which can be useful
for a wide range of tasks including land cover classification,
object counting or detection. However, most of the available
methodologies are task-specific, thus inhibiting generic and easy
access to the information contained in remote sensing data. As
a consequence, accurate remote sensing product generation still
requires expert knowledge. With RSVQA, we propose a system to
extract information from remote sensing data that is accessible to
every user: we use questions formulated in natural language and
use them to interact with the images. With the system, images
can be queried to obtain high level information specific to the
image content or relational dependencies between objects visible
in the images. Using an automatic method introduced in this
article, we built two datasets (using low and high resolution data)
of image/question/answer triplets. The information required to
build the questions and answers is queried from OpenStreetMap
(OSM). The datasets can be used to train (when using supervised
methods) and evaluate models to solve the RSVQA task. We
report the results obtained by applying a model based on
Convolutional Neural Networks (CNNs) for the visual part and on
a Recurrent Neural Network (RNN) for the natural language part
to this task. The model is trained on the two datasets, yielding
promising results in both cases.
Index Terms —Visual Question Answering, Deep learning,
Dataset, Natural Language, Convolution Neural Networks, Re-
current Neural Networks, Very High Resolution, OpenStreetMap
I. I NTRODUCTION
REMOTE sensing data is widely used as an indirect
source of information. From land cover/land use to
crowd estimation, environmental or urban area monitoring,
remote sensing images are used in a wide range of tasks
of high societal relevance. For instance, remote sensing data
can be used as a source of information for 6 of the 17 sus-
tainable development goals as defined by the United Nations
[1]. Due to the critical nature of the problems that can be
addressed using remote sensing data, significant effort has
been made to increase its availability in the last decade. For
instance, Sentinel-2 satellites provide multispectral data with
a relatively short revisiting time, in open-access. However,
while substantial effort has been dedicated to improving the
means of direct information extraction from Sentinel-2 data
Sylvain Lobry, Diego Marcos, Jesse Murray and Devis Tuia are with
Laboratory of Geo-Information Science and Remote Sensing, Wageningen
University, The Netherlands email: work@sylvainlobry.com
Classification
Is it a rural or urban area?Regression
How many buildings are there?
Detection
Is there a road?Classical tasks
Regression
What is the area covered by small
buildings?Detection
Is there a road at the top of the image?Specific tasks
Regression / Detection
What is the number of roads next to a
park?Detection
Is there a building next to a parking?Mix of tasksFig. 1. Example of tasks achievable by a visual question answering model
for remote sensing data.
in the framework of a given task (e.g. classification [2], [3]),
the ability to use remote sensing data as a direct source of
information is currently limited to experts within the remote
sensing and computer vision communities. This constraint,
imposed by the technical nature of the task, reduces both the
scale and variety of the problems that could be addressed with
such information as well as the number of potential end-users.
This is particularly true when targeting specific applications
(detecting particular objects, e.g.thatched roofs or buildings in
a developing country [4]) which would today call for important
research efforts. The targeted tasks are often multiple and
changing in the scope of a project calls for strong expert
knowledge, limiting the information which can be extracted
from remote sensing data. To address these constraints, we
introduce the problem of visual question answering (VQA)
for remote sensing data.arXiv:2003.07333v2 [cs.CV] 14 May 2020
PRE-PRINT. FINAL VERSION IN IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2
VQA is a new task in computer vision, introduced in its
current form by [5]. The objective of VQA is to answer a
free-form and open-ended question about a given image. As
the questions can be unconstrained, a VQA model applied
to remote sensing data could serve as a generic solution
to classical problems involving remote sensing data (e.g.
”Is there a thatched roof in this image?” for thatched roof
detection), but also very specific tasks involving relations
between objects of different nature (e.g. ”Is there a thatched
roof on the right of the river?”). Examples of potential
questions are shown in Figure 1.
To the best of our knowledge, this is the first time (after
the first exploration in [6]) that VQA has been applied to
extract information from remote sensing data. It builds on the
task of generating descriptions of images through combining
image and natural language processing to provide the user
with easily accessible, high-level semantic information. These
descriptions are then used for image retrieval and intelligence
generation [7]. As seen in this introduction, VQA systems rely
on the recent advances in deep learning. Deep learning based
methods, thanks to their ability to extract high-level features,
have been successfully developed for remote sensing data as
reviewed in [8]. Nowadays, this family of methods is used to
tackle a variety of tasks; for scene classification, an early work