Horizontal vs verticle image

I was taking photos for my website and had camera on tripod, close up setting, pointing down at object. when i checked photos they were in horizontal image, i then had to change battery, removed camera from tripod re atached same way/position and took more photos and when i checked those they were in the portrait/vertical image, I changed no settings put camera in exact same position. why did it change orientation from horizontal to portrait/vertical?

You should probably name camera/lens, it might matter when it comes to "settings".

There is a sensor in camera which detects if the long edge of the frame is parallel to the ground, or at right angles...it gets fooled with the lens pointed straight down instead of pointed forward.

camera is a t4i,lens efs18-135mm after i noticed vertical pictures I removed camera from tripod and looked at images on TV, then attached camera back to tripod in same orientation, pointing down and it took next 35 images in horizontal still kinda confused

My 7DII has a indicator for 'level'...I can make that indicator move from 'horizontal' to 'vertical' or points in between, all while the lens is aimed DOWN toward the floor. The level sensor is not designed for that orientation to be sensed.

As Wilt said there is a sensor in the camera that detects the vertical orientation of the body. This is will work most efficiently when the sensor plane is at 90° to the ground. As you rotate the plane of the sensor away from the vertical the sensor starts to have a harder time telling which way is up. When you get the camera over so that the plane of the sensor is parallel to the ground, it gets to the point where it cannot detect the orientation at all. So you will tend to get a random output from the sensor. Once the camera is set up and locked in position that random output is unlikely to change, but make any small adjustment to the camera position and the random output may change.

Alan