planet.py

import torch.nn as nn
from torchvision.models import resnet18

class PlaNetModel(nn.Module):
    def __init__(self, num_cells):
        super().__init__()
        self.backbone = resnet18(weights=None)
        self.backbone.fc = nn.Linear(self.backbone.fc.in_features, num_cells)

    def forward(self, x):
        return self.backbone(x)

def decode_tile_to_latlon(cell_idx):
    tile_size_lat = 180 / 316  # ~0.57 degrees (180° range / sqrt(100k))
    tile_size_lon = 360 / 316  # ~1.14 degrees

    row = cell_idx // 316
    col = cell_idx % 316

    lat = 90 - row * tile_size_lat - tile_size_lat / 2
    lon = -180 + col * tile_size_lon + tile_size_lon / 2

    return round(lat, 6), round(lon, 6)