Pompey took the lead through Jamal Lowe in the 15th minute and missed chances to double their lead before the break, with the visitors striking back in the second half through Kevin van Veen.
Gallen felt that on the balance of play the draw was a fair result as his side slipped out of the play-off places.
“We haven’t had many draws,” he said.
“It was a game of two halves. We played really well in the first half and imposed ourselves on them and we deservedly went ahead.
“On a good day, we could have perhaps got another one and I always felt like we would have needed another one today if we were going to beat Scunthorpe.
“In the second half, Scunthorpe got back into it a bit more and had some more chances.
“Goals give everyone confidence and the goal gave them the confidence.
“A draw in the end was fair but it was a fantastic battling performance from our team. They showed a fantastic attitude and we pride ourselves on that.”
Scunthorpe should have gone ahead in the second minute when Tom Hopper was played in on goal but he squandered the chance after failing to get his shot away quickly enough.
And then Pompey made sure the visitors rued their miss when they went ahead through Lowe in the 15th minute.
The winger nicked the ball off Josh Morris in the Scunthorpe area before he drilled his effort into the bottom corner.
The home side could have doubled their first-half lead when captain Brett Pitman struck his effort just past the post.
But Scunthorpe pegged Pompey back in the 53rd minute after Van Veen rifled his shot into the back of the net from close range from Hopper’s cross.
Manager Graham Alexander praised his side’s fighting spirit to get themselves back in the game.
“It was a very close game,” he said.
“I thought it was a very scrappy first half where Portsmouth changed their formation to combat and nullify us.
“But they got the goal early on and we had to make a few points at half-time but the players knew themselves that they had to step it up.
“They had to show a bit more composure and do the basics well and, to be fair, I thought in the second-half that we dominated and could have got the winner.
“So credit to the players as they have shown their quality.
“The second half was really like us. We were on the front foot and bossed the game.”
Morecambe have no fresh injury concerns ahead of Tuesday's Sky Bet League Two home clash with Colchester.