Our Ancients built Hindu Temples in a Straight line (From Kedarnath to Rameswaram - all are Lord Shiva temples), at that time without having proper Maps and Satellite's how can they built in straight line? Our ancestors known about Earth Geometry or Any one helped?
It is not that these temples were built by looking geometry of earth or using some advanced technology to map latitude and longitude.
These are Tirtha sthalas and they are not like modern day temples where they can be built anywhere (looking latitudes and longitudes). Tirthasthalas are those where some divine story happened there and temple is built at that place in the rememberance of that story and recognizing the special divinity residing there.
Kedarnath is the place where Nara-Narayana established Shiva Linga as discussed in answer here. Similarly in Rameshwaram Rama established Shiva Linga near Setu Bandha area as discussed in answer here.. Sri Kalahasti is the place where Vayu established Shiva Linga as discussed in answer here And similarly all Tirtha sthalas are those place where some divine things happened there and thus temple is built there.
The point is these Temples aren't built by selecting such places where Latitude and Longitude matches. They are established where some divine story happened. So, there is no question of using some technologies to match latitude and longitude.
But how is it possible that they all came to lie on straight line? We can just say this is a divine coincidence and it's all Shiva's plan. So, the stories happened on particular place and temples were built there. It's all wish of Shiva.
Lord Siva Temples in India on almost same Longitude
- Kedarnath – Kedarnath Temple (30.7352° N, 79.0669)
- Kaleshwaram – Kaleshwara Mukteeshwara swamy Temple (18.8110, 79.9067)
- Srikalahati – Srikalahasti Temple (13.749802, 79.698410)
- Kanchipuram – Ekambareswarar Temple (12.847604, 79.699798)
- Thiruvanaikaval – Jambukeswara Temple (10.853383, 78.705455)
- Tiruvannamalai – Annamalaiyar Temple (12.231942, 79.067694)
- Chidambaram – Nataraja Temple (11.399596, 79.693559)
- Rameswaram – Ramanathaswamy Temple(9.2881, 79.3174)
The five temples were built according to the yogic sciences, and are placed in a certain geographic alignment with each other, so that the entire region reverberated with the possibility they offered.