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tion and their fine-grained descriptions are well aligned. |
To show this, we randomly selected 1000 overhead images |
from our training set, and compute their Sat2Cap embed- |
dings. For a given text query, we generate the CLIP[1] text |
embedding and compute its similarity with all images in the |
test set. Figure 1 shows examples of 4 closest overhead im- |
ages retrieved for a given query. |
We experiment with small perturbations of prompts to |
analyze how our retrieval results change with minute vari- |
ations of query. We see in Figure 1, the prompt “people |
driving cars” retrieves city or residential areas. However, |
replacing the phrase “driving cars” with “riding horses” re- |
trieves locations with farmland. Similarly, the prompt “per- |
son on a long hike” exclusively retrieves mountainous re- |
gions, while the prompt “person on a long run” retrieves |
images that looks like trails nearby residential areas. Hence, |
Sat2Cap embeddings demonstrate a good understanding of |
fine-grained variations of textual concepts. |
B. More Large-scale Textual Maps |
We create country-level maps of England and Nether- |
lands for four different prompts: a) Farmers harvesting |
crops, b) Cars stuck in traffic, c) Animals grazing in the |
fields, and d) People fishing on a boat. To generate the tex- |
tual maps for each prompt, we compute the Sat2Cap em- |
beddings for all images of the country and compute its sim- |
ilarity with the CLIP text embeddings of the given prompt. |
We normalize the similarities and plot those to create the |
textual maps. Figure 2 shows textual maps of Netherlands |
and England for each prompt. We also placed a landcover |
map on the bottom of each text map as a reference of places |
with likely activations for the given prompt. |
By comparing with the respective landcover maps, we |
see that the Sat2Cap embeddings activates reasonable loca- |
tions on a map for a given prompt. For example, the prompt |
“Farmers harvesting crops” gets activated mostly in crop- |
land, while the prompt “Cars stuck in traffic” is activated |
in urban areas. Similarly, the textual maps of the prompts |
“Animals grazing in the fields”, and “People fishing on a |
boat” look similar to the rangeland and water landcover re- |
spectively. In (d), we see high activations in the top-left |
corner for England, which does not match the water land- |
cover. This region is the Lake District, which has numerousbeautiful lakes. |
C. Dynamic Caption Generation |
We take a single overhead image and show the dynamic |
captions Sat2Cap embedding can generate. Figure 3 shows |
our results on a test image at four different temporal set- |
tings. The generated captions capture both the semantic |
concepts from the given image as well as the temporal con- |
cepts that are added to it. As you move from May to Decem- |
ber, the concepts of winter become more prominent in the |
captions. Similarly, as you move from 10:00 am to 11:00 |
pm, we see the concepts associated with night are better |
highlighted. One interesting observation is that we are not |
getting trivial changes, such as simply adding in winter or |
at night to the captions. Rather, the entire concept that the |
captions describe also changes. |
D. Dataset |
We introduced a cross-view dataset with overhead im- |
ages and co-located ground-level images taken from the |
YFCC100M [2] dataset. Figure 4 shows a few samples |
from our dataset. The ground-level images provide us with |
detailed fine-grained concepts of a location that cannot be |
directly inferred when looking at the overhead imagery. |
E. Overhead to Ground Image Retrieval |
In figure 5, we show additional results of overhead- |
to-ground image retrieval. We see that Sat2Cap embed- |
dings accurately relate overhead imagery with fine-grained |
ground-level concepts. An interesting thing to note is that |
the relationship is not based primarily on visual feature |
matching but rather based on agreement of concepts. For |
example, the overhead image of a running track retrieves |
images of people playing different sports, while an image |
over the ocean retrieves images of people enjoying various |
water sports. |
References |
[1] Alec Radford, Jong Wook Kim, Chris Hallacy, Aditya |
Ramesh, Gabriel Goh, Sandhini Agarwal, Girish Sastry, |
Amanda Askell, Pamela Mishkin, Jack Clark, et al. Learn- |
ing transferable visual models from natural language supervi- |
sion. In International conference on machine learning , pages |
8748–8763. PMLR, 2021. 1 |
[2] Bart Thomee, David A Shamma, Gerald Friedland, Benjamin |
Elizalde, Karl Ni, Douglas Poland, Damian Borth, and Li-Jia |
Li. Yfcc100m: The new data in multimedia research. Com- |
munications of the ACM , 59(2):64–73, 2016. 1 |
1arXiv:2307.15904v1 [cs.CV] 29 Jul 2023 |
Figure 1: Top-4 text-to-overhead retrieval: We retrieve the top-4 closest overhead image from a given text prompt. Our |
results show that Sat2Cap embeddings can accurately relate geolocations with fine-grained textual prompts. |
2 |
Figure 2: Zero-shot map of countries: We show the textual maps of England and Netherlands for different queries. We |
also show a landcover map as a guide for plausible locations where the query is likely to be activated. In (d), we see high |
activations in the top-left corner of england which lies in the “Lake District National Park”. |
3 |
Figure 3: Dynamic Caption Generation: Our Sat2Cap embeddings dynamically adapt to temporal manipulations, facilitat- |
ing dynamic caption generation. |
Figure 4: Examples of co-located overhead and ground images in our dataset. The ground-level images describe more |
detailed concepts of the given locations than their overhead counterparts. |
4 |
Figure 5: Top-9 overhead-to-ground retrieval : Our model is capable of inferring fine-grained concepts of ground-level |
scenes through overhead imagery. Sat2Cap accurately retrieves probable concepts for a given geolocation using an overhead |
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