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3 Articles
Posted by Dirk Alvermann on

Use Case: “Model Booster”

Release 1.10.1

In our example we want to improve our HTR model for the Responsa. This is an HTR model that can read 17th century Kurrent documents. In the search for a possible base model, you can find two candidates in the “public models” of Transkribus: “German Kurrent M1+” from the Transkribus Team and “German_Kurrent_XVI-XVIII_M1” from Tobias Hodel. Both could fit. But the test on the Sample Compare shows that “German_Kurrent_XVI-XVIII_M1” performed better with a predicted average CER of 9.3% on our sample set.

Therefore “German_Kurrent_XVI-XVIII_M1” was chosen as the base model for the training. Afterwards the Ground Truth of the Responsa (108.000 words) and also the Validation Set of our old model was added. The average CER of our HTR model has improved considerably after the Base Model Training, from 7.3% to 6.6%.As you can see in the graph, the base model on the test set reads much worse than the original model, but the hybrid of the two is better than either one. The improvement of the model can be seen in each of the years tested and is up to 1%.

Posted by Dirk Alvermann on

Combining Models

Release 1.10.1

The longer you train HTR models yourself, the more you will be interested in the possibility of combining models. For example, you may want to combine several special models for individual writers or models that are specialized in particular fonts or languages.

To achieve a combination of models there are different possibilities. Here I would like to introduce a technique that works in my experience especially well for very large generic models – the “Model Booster“.

You start a base model training and use a powerful, foreign HTR model as base model and your own ground truth as train set. But before you start, two recommendations:

a) take a close look at the characteristics of the base model you are using (for how long is it trained, for which font style and which language?) – they have to match those of your own material as much as possible.

b) if possible try to predict the performance of the base model on your own material and then choose the base model with the best performance. Such a prediction can be made quite easily using the Sample Compare function. Another possibility is to test the basemodel with the Andvanced Compare on your own test set.

Posted by Anna Brandt on

Transcribing without layout analysis?

Release 1.10.1

We have emphasized in previous posts how important LA is. Without it, an HTR model, no matter how good it is, has no chance of transcribing a text properly. The steps of automatic LA (or a P2PaLA model) and HTR are usually initiated separately. Now we noticed that when an HTR model runs over a completely new or unedited page, the program automatically executes an LA.

This LA runs with the default settings of CITLab-Advanced LA. On pure pages, fewer lines have to be merged and sometimes more than one text region is recognized.

But it also means that only horizontal text is recognized. We had the same problem with our P2PaLA models. Everything that is slanted or vertical cannot be recognized this way. To do this, the LA must be initiated manually, with the setting ‘Text Orientation’ set to ‘Heterogeneous’.

Interestingly, the HTR results are better with this method than with an HTR that has been run over a corrected layout analysis. We have calculated the CER for some pages to show this.

Thus this method is a very good alternative, especially for pages with an uncomplicated layout. You save time, because you only have to initiate one process, and in the end you have a better result.