The marking scheme for the Officer Intelligence Rating (OIR) Test Picture Perception and Description (PPDT) Test in the NDA exam is designed to assess the candidate's ability to observe and comprehend a given picture, as well as their ability to express their thoughts and ideas coherently and effectively.

The PPDT test consists of a series of random pictures displayed for a short duration (around 30 seconds) followed by a given time (around 3 minutes) to write a story or description based on the picture. The marking scheme for this test generally includes the following components:

1. Content: The content of the story or description is given the most weightage. It assesses the candidate's ability to understand the situation depicted in the picture, the characters involved, and the events taking place. The content should be logical, relevant, and coherent.

2. Theme: The story or description should have a clear theme or message. It should demonstrate the candidate's ability to create a meaningful narrative and convey a purpose or moral.

3. Organization: The candidate's ability to organize their thoughts and present them in a structured manner is also evaluated. The story or description should have a proper beginning, middle, and end. It should flow smoothly and be easy to understand.

4. Language and Grammar: The use of appropriate language, grammar, and vocabulary is important. The candidate's ability to express their ideas effectively, use correct grammar, and maintain a good writing style is assessed.

5. Originality: The marking scheme also considers the candidate's originality and creativity in their story or description. The ability to think out-of-the-box and come up with unique ideas or perspectives is valued.

It is important to note that there is no fixed marking scheme or specific marks allotted for each component. The evaluation is subjective, and the assessors look for overall qualities and skills in the candidate's response. Therefore, it is advisable to focus on understanding the picture, creating a coherent story or description, and expressing thoughts clearly and effectively.