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data labels are not available. [9] rotates an image and then
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trains a model to predict the rotation angle. [48] trains a
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network to perform colorization of a grayscale image. [26]
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represents an image as a grid, permuting the grid and then
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predicting the permutation index. In this study, we use geo-location classification as a pre-text task, in which a deep
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network is trained to predict a coarse geo-location of where
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in the world the image might come from.
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Contrastive Learning Recent self-supervised contrastive
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learning approaches such as MoCo [13], MoCo-v2 [3], Sim-
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CLR [2], PIRL [22], and FixMatch [32] have demonstrated
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superior performance and have emerged as the fore-runner
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on various downstream tasks. The intuition behind these
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methods are to learn representations by pulling positive
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image pairs from the same instance closer in latent space
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while pushing negative pairs from difference instances fur-
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ther away. These methods, on the other hand, differ in the
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type of contrastive loss, generation of positive and negative
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pairs, and sampling method.
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Although growing rapidly in self-supervised learning
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area, contrastive learning methods have not been explored
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on large-scale remote sensing dataset. In this work, we pro-
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vide a principled and effective approach for improving rep-
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resentation learning using MoCo-v2 [13] for remote sensing
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data as well geo-located conventional datasets.
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Unsupervised Learning in Remote Sensing Images Un-
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like in traditional computer vision areas, unsupervised
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learning on remote sensing domain has not been studied
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comprehensively. Most of the studies utilize small-scale
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datasets specific to a small geographical region [4, 17, 30,
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15, 19], a few classes [35, 25] or a highly-specific modal-
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ity, i.e. hyperspectral images [23, 47]. Most of these
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studies focus on the UCM-21 dataset [45] consisting of
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less than 1,000 images from 21 classes. A more recent
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study [36] proposes large-scale weakly supervised learn-
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ing using a multi-modal dataset consisting of satellite im-
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ages and paired geo-located wikipedia articles. While be-
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ing effective, this method requires each satellite image to
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be paired to its corresponding article, limiting the number
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of images that can be used.
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Geography-aware Computer Vision Geo-location data
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has been studied extensively in prior works. Most of these
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2
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"gsd": "img_width": "img_height": "country_code": "cloud_cover": “timestamp": 2.10264849663 2421 2165 IND 6 2015-11-02 T05:44:14Z2.06074237823 2410 2156 IND 0 2016-03-09 T05:25:30Z1.9968634 2498 2235 IND 1 2017-02-02 T05:47:02Z2.2158575 2253 2015 IND 0 2017-02-27 T05:24:30Z1.24525177479 4016 3592 IND 0 2015-04-09 T05:36:04Z1.4581833 3400 3041 IND 2 2016-12-28 T05:57:06Z1.2518295 4003 3581 IND 0 2017-04-12 T05:51:49ZFigure 2: Images over time concept in the fMoW dataset. The metadata associated with each image is shown underneath.
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We can see changes in contrast, brightness, cloud cover etc. in the images. These changes render spatially aligned images
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over time useful for constructing additional positives.
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-45.829337,
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170.730800,
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Te Matai,
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New Zealand,
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Otago10.595525,
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76.041355,
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Guruvayoor ,
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India,
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Kerala,
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Thrissur29.008740,
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-81.963415,
|
Lake W eir,
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Florida,Marion
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United States28.318038,
|
-81.540688,
|
Celebration,
|
United States,
|
Florida,Osceola21.881018,
|
-102.275360,
|
Aguascalientes,
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México,
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Aguascalientes,
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Aguascalientes59.61 1778,
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-151.449966,
|
Homer ,
|
United States,
|
Alaska,
|
Kenai
|
Peninsula Borough37.345989,
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-77.645680,
|
Beach,
|
United States,
|
Virginia,
|
Chesterfield37.303518,
|
-121.897773,
|
San Jose,
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United States,
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California,
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Santa Clara22.494622,
|
114.028447,
|
⼤浪,
|
⾹港,
|
新界,
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元朗區27.876676,
|
-82.798231,
|
Walsingham,
|
United States,
|
Florida,
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Pinellas
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-18.646245,
|
24.614868,
|
Botswana,
|
Chobe
|
Figure 3: Some examples from GeoImageNet dataset. Below each image, we list their latitudes, longitudes, city, country
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name. In our study, we use the latitude and longitude information for unsupervised learning. We recommend readers to
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