WhiteRoadLines: Dataset of 27,025 images (256x256 pixeles at 0.15 m/ pixel) containing representative road lines and markings labelled for multi-class semantic segmentation

The dataset consists of 27,025 PNG images (256x256 pixels) of high resolution aerial orthoimages at 0,15 m/pixel of resolution. The images contain information related to representative road lines and markings found on highway pavement and is labelled for multi-class semantic segmentation with tree classes of white roadlines and markings: (1) continuous line (black color), (2) dashed line (dark gray color) and (3) separation of entry and exit lanes (light gray color), together with (4) the background (white color).  
The dataset has been created in the framework of the SROADEX project to train a multiclass semantic segmentation process based on Deep Learning.The data have been generated using scripts developed in Python using Open Source libraries (GDAL/OGR and MapScript) for rasterization of vector cartography representing the three different types of white road lines. This cartography has been obtained from Spanish official sources (National Geographic Institute) that we haverevised and edited in a meticulous and systematic way to verify that the road lines are represented on the cartography according to the orthoimages, available on January 1, 2022 in the download center of the National Center of Geographic Information (CNIG). 
In the digitisation process, 46 homogeneously distributed areas of Spain have been selected. The orthoimages used have been resampled from the original resolution of 0,25m/pixel to 0,15m/pixel, as this is closer to the width of two of the three classes of white lines in the dataset. It resulted in 80% of the images for training (21622), 10% for validation (2702) and 10% for testing (2701). The following table summarises the number of pixels of each category included in each of the three sub-datasets

Set              Nº images   Class_1 (continuous line)   Class_2 (discontinuous line) Class_3 (line defining highway entrance or exit)  Class_4 (background)
Train                 21,622      27,633,537                         4,543,552                               3,284,380                                                           1,381,557,923
Validation           2,702        3,433,103                            570,741                                  395,646                                                               172,678,782
Test                    2,701        3,435,072                            536,838                                  429,527                                                               172,611,299
Total                 27,025      34,501,712                         5,651,131                               4,109,553                                                            1,726,848,004